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Eliminating Code Overhead Jake Wharton

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CPU

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Memory CPU

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Memory CPU I/O

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Memory CPU I/O Battery

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Battery Memory CPU I/O

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Battery Battery Memory CPU I/O

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Battery Battery Memory CPU I/O

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Battery Battery Memory CPU I/O

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Battery Battery Battery Memory CPU I/O

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Battery Battery Battery Memory CPU I/O

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Battery Battery Battery Memory CPU I/O

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Memory CPU I/O

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Memory CPU I/O

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• Do not nest multi-pass layouts • Lazily compute complex data when needed • Cache heavy computational results for re-use • Consider RenderScript for performance • Keep work off of the main thread Memory CPU I/O

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• Use object pools and caches to reduce churn • Be mindful of the overhead of enums • Do not allocate inside the draw path • Use specialized collections instead of JDK collections when appropriate (SparseArray) Memory CPU I/O

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Memory CPU I/O • Batch operations with reasonable back-off policies • Use gzip or binary serialization format • Cache data offline with TTLs for reloading • Use JobScheduler API to batch across OS

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I/O Memory CPU What's next after macro?

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I/O Memory CPU What's next after macro? • Move on to so-called micro

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I/O Memory CPU What's next after macro? • Move on to so-called micro • Spectrum of optimizations, not binary

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I/O Memory CPU What's next after macro? • Move on to so-called micro • Spectrum of optimizations, not binary • Do not blindly apply to everything, only when appropriate

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I/O Memory CPU What's next after macro? • Move on to so-called micro • Spectrum of optimizations, not binary • Do not blindly apply to everything, only when appropriate • Multiple micro-optimizations can improve like a macro

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public List names(List users) {
 List names = new ArrayList<>();
 for (User user : users) {
 names.add(user.name);
 }
 return unmodifiableList(names);
 }

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public List names(List users) {
 List names = new ArrayList<>();
 for (User user : users) {
 names.add(user.name);
 }
 return unmodifiableList(names);
 }

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public List names(List users) {
 List names = new ArrayList<>();
 for (User user : users) {
 names.add(user.name);
 }
 return unmodifiableList(names);
 }

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public List names(List users) {
 List names = new ArrayList<>();
 for (User user : users) {
 names.add(user.name);
 }
 return unmodifiableList(names);
 }

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public List names(List users) {
 List names = new ArrayList<>();
 for (User user : users) {
 names.add(user.name);
 }
 return unmodifiableList(names);
 }

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public List names(List users) {
 List names = new ArrayList<>();
 for (User user : users) {
 names.add(user.name);
 }
 return unmodifiableList(names);
 }

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public List names(List users) {
 List names = new ArrayList<>();
 for (User user : users) {
 names.add(user.name);
 }
 return unmodifiableList(names);
 }

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public List names(List users) {
 List names = new ArrayList<>();
 for (User user : users) {
 names.add(user.name);
 }
 return unmodifiableList(names);
 }

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public List names(List users) {
 List names = new ArrayList<>();
 for (User user : users) {
 names.add(user.name);
 }
 return unmodifiableList(names);
 }

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public List names(List users) {
 List names = new ArrayList<>();
 for (User user : users) {
 names.add(user.name);
 }
 return unmodifiableList(names);
 }

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public List names(List users) {
 List names = new ArrayList<>();
 for (User user : users) {
 names.add(user.name);
 }
 return unmodifiableList(names);
 }

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public List names(List users) {
 List names = new ArrayList<>();
 for (User user : users) {
 names.add(user.name);
 }
 return unmodifiableList(names);
 }

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public List names(List users) {
 List names = new ArrayList<>();
 for (User user : users) {
 names.add(user.name);
 }
 return unmodifiableList(names);
 }

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public List names(List users) {
 List names = new ArrayList<>();
 for (User user : users) {
 names.add(user.name);
 }
 return unmodifiableList(names);
 }

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public List names(List users) {
 List names = new ArrayList<>();
 for (User user : users) {
 names.add(user.name);
 }
 return unmodifiableList(names);
 }

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public List names(List users) {
 List names = new ArrayList<>();
 for (User user : users) {
 names.add(user.name);
 }
 return unmodifiableList(names);
 }

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public List names(List users) {
 List names = new ArrayList<>();
 for (User user : users) {
 names.add(user.name);
 }X
 return unmodifiableList(names);
 }X

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public List names(List users) {
 List names = new ArrayList<>();
 for (User user : users) {
 names.add(user.name);
 }X
 return unmodifiableList(names);
 }X

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public List names(List users) {
 List names = new ArrayList<>();
 for (User user : users) {
 names.add(user.name);
 }X
 return unmodifiableList(names);
 }X

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public List names(List users) {
 List names = new ArrayList<>();
 for (User user : users) {
 names.add(user.name);
 }X
 return unmodifiableList(names);
 }X

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public List names(List users) {
 List names = new ArrayList<>();
 for (User user : users) {
 names.add(user.name);
 }X
 return unmodifiableList(names);
 }X

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public List names(List users) {
 List names = new ArrayList<>();
 for (User user : users) {
 names.add(user.name);
 }X
 return unmodifiableList(names);
 }X

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public List names(List users) {
 List names = new ArrayList<>();
 for (User user : users) {
 names.add(user.name);
 }X
 return unmodifiableList(names);
 }X

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public List names(List users) {
 List names = new ArrayList<>();
 for (User user : users) {
 names.add(user.name);
 }
 return unmodifiableList(names);
 }

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public List names(List users) {
 List names = new ArrayList<>();
 for (User user : users) {
 names.add(user.name);
 }
 return unmodifiableList(names);
 }

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public List names(List users) {
 List names = new ArrayList<>();
 for (User user : users) {
 names.add(user.name);
 }
 return unmodifiableList(names);
 }

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public List names(List users) {
 List names = new ArrayList<>();
 for (User user : users) {
 names.add(user.name);
 }
 return unmodifiableList(names);
 }

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public List names(List users) {
 List names = new ArrayList<>();
 for (User user : users) {
 names.add(user.name);
 }
 return unmodifiableList(names);
 }

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public List names(List users) {
 List names = new ArrayList<>();
 for (User user : users) {
 names.add(user.name);
 }
 return unmodifiableList(names);
 }

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public List names(List users) {
 List names = new ArrayList<>();
 for (User user : users) {
 names.add(user.name);
 }
 return unmodifiableList(names);
 }

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public List names(List users) {
 List names = new ArrayList<>();
 for (User user : users) {
 names.add(user.name);
 }
 return unmodifiableList(names);
 }

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public List names(List users) {
 List names = new ArrayList<>();
 for (User user : users) {
 names.add(user.name);
 }
 return unmodifiableList(names);
 }

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public List names(List users) {
 List names = new ArrayList<>();
 for (User user : users) {
 names.add(user.name);
 }
 return unmodifiableList(names);
 }

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public List names(List users) {
 List names = new ArrayList<>();
 for (User user : users) {
 names.add(user.name);
 }X
 return unmodifiableList(names);
 }X

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public List names(List users) {
 List names = new ArrayList<>();
 for (User user : users) {
 names.add(user.name);
 }X
 return unmodifiableList(names);
 }X

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public List names(List users) {
 List names = new ArrayList<>();
 for (User user : users) {
 names.add(user.name);
 }X
 return unmodifiableList(names);
 }X

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public List names(List users) {
 List names = new ArrayList<>();
 for (User user : users) {
 names.add(user.name);
 }X
 return unmodifiableList(names);
 }X

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public List names(List users) {
 List names = new ArrayList<>();
 for (User user : users) {
 names.add(user.name);
 }X
 return unmodifiableList(names);
 }X

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public List names(List users) {
 List names = new ArrayList<>();
 for (User user : users) {
 names.add(user.name);
 }X
 return unmodifiableList(names);
 }X

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public List names(List users) {
 List names = new ArrayList<>();
 for (User user : users) {
 names.add(user.name);
 }X
 return unmodifiableList(names);
 }X

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public List names(List users) {
 List names = new ArrayList<>();
 for (User user : users) {
 names.add(user.name);
 }
 return unmodifiableList(names);
 }

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public List names(List users) {
 List names = new ArrayList<>();
 for (User user : users) {
 names.add(user.name);
 }
 return unmodifiableList(names);
 }

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public List names(List users) {
 List names = new ArrayList<>();
 for (User user : users) {
 names.add(user.name);
 }
 return unmodifiableList(names);
 }

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public List names(List users) {
 List names = new ArrayList<>();
 for (User user : users) {
 names.add(user.name);
 }
 return unmodifiableList(names);
 }

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public List names(List users) {
 List names = new ArrayList<>();
 for (User user : users) {
 names.add(user.name);
 }
 return unmodifiableList(names);
 }

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public List names(List users) {
 List names = new ArrayList<>();
 for (User user : users) {
 names.add(user.name);
 }
 return unmodifiableList(names);
 }

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public List names(List users) {
 List names = new ArrayList<>();
 for (User user : users) {
 names.add(user.name);
 }
 return unmodifiableList(names);
 }

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public List names(List users) {
 List names = new ArrayList<>();
 for (User user : users) {
 names.add(user.name);
 }
 return unmodifiableList(names);
 }

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public List names(List users) {
 List names = new ArrayList<>();
 for (User user : users) {
 names.add(user.name);
 }
 return unmodifiableList(names);
 }

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public List names(List users) {
 List names = new ArrayList<>();
 for (User user : users) {
 names.add(user.name);
 }
 return unmodifiableList(names);
 }

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public List names(List users) {
 List names = new ArrayList<>();
 for (User user : users) {
 names.add(user.name);
 }
 return unmodifiableList(names);
 }

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public List names(List users) {
 List names = new ArrayList<>();
 for (User user : users) {
 names.add(user.name);
 }
 return unmodifiableList(names);
 }

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public List names(List users) {
 List names = new ArrayList<>();
 for (User user : users) {
 names.add(user.name);
 }
 return unmodifiableList(names);
 }

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public List names(List users) {
 List names = new ArrayList<>();
 for (User user : users) {
 names.add(user.name);
 }X
 return unmodifiableList(names);
 }X

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public List names(List users) {
 List names = new ArrayList<>(users.size());
 for (User user : users) {
 names.add(user.name);
 }X
 return unmodifiableList(names);
 }X

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public List names(List users) {
 List names = new ArrayList<>(users.size());
 for (User user : users) {
 names.add(user.name);
 }X
 return unmodifiableList(names);
 }X

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public List names(List users) {
 List names = new ArrayList<>(users.size());
 for (User user : users) {
 names.add(user.name);
 }X
 return unmodifiableList(names);
 }X

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public String names(List users) {
 StringBuilder builder = new StringBuilder();
 for (User user : users) {
 if (builder.length() > 0) builder.append(", ");
 builder.append(user.name);
 }X
 return builder.toString();
 }X

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public String names(List users) {
 StringBuilder builder = new StringBuilder();
 for (User user : users) {
 if (builder.length() > 0) builder.append(", ");
 builder.append(user.name);
 }X
 return builder.toString();
 }X

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public String names(List users) {
 StringBuilder builder = new StringBuilder();
 for (User user : users) {
 if (builder.length() > 0) builder.append(", ");
 builder.append(user.name);
 }X
 return builder.toString();
 }X

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public String names(List users) {
 StringBuilder builder = new StringBuilder();
 for (User user : users) {
 if (builder.length() > 0) builder.append(", ");
 builder.append(user.name);
 }X
 return builder.toString();
 }X

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public String names(List users) {
 StringBuilder builder = new StringBuilder();
 for (User user : users) {
 if (builder.length() > 0) builder.append(", ");
 builder.append(user.name);
 }X
 return builder.toString();
 }X

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public String names(List users) {
 StringBuilder builder = new StringBuilder();
 for (User user : users) {
 if (builder.length() > 0) builder.append(", ");
 builder.append(user.name);
 }X
 return builder.toString();
 }X

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public String names(List users) {
 StringBuilder builder = new StringBuilder();
 for (User user : users) {
 if (builder.length() > 0) builder.append(", ");
 builder.append(user.name);
 }X
 return builder.toString();
 }X Jimmy•McNulty

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public String names(List users) {
 StringBuilder builder = new StringBuilder();
 for (User user : users) {
 if (builder.length() > 0) builder.append(", ");
 builder.append(user.name);
 }X
 return builder.toString();
 }X Jimmy•McNulty

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public String names(List users) {
 StringBuilder builder = new StringBuilder();
 for (User user : users) {
 if (builder.length() > 0) builder.append(", ");
 builder.append(user.name);
 }X
 return builder.toString();
 }X Jimmy•McNulty

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Jimmy•McNulty public String names(List users) {
 StringBuilder builder = new StringBuilder();
 for (User user : users) {
 if (builder.length() > 0) builder.append(", ");
 builder.append(user.name);
 }X
 return builder.toString();
 }X

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Jimmy•McNulty public String names(List users) {
 StringBuilder builder = new StringBuilder();
 for (User user : users) {
 if (builder.length() > 0) builder.append(", ");
 builder.append(user.name);
 }X
 return builder.toString();
 }X Jimmy•McNulty,•

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public String names(List users) {
 StringBuilder builder = new StringBuilder();
 for (User user : users) {
 if (builder.length() > 0) builder.append(", ");
 builder.append(user.name);
 }X
 return builder.toString();
 }X Jimmy•McNulty,• Jimmy•McNulty,•

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public String names(List users) {
 StringBuilder builder = new StringBuilder();
 for (User user : users) {
 if (builder.length() > 0) builder.append(", ");
 builder.append(user.name);
 }X
 return builder.toString();
 }X Jimmy•McNulty,• Stringer•Bell Jimmy•McNulty,•

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public String names(List users) {
 StringBuilder builder = new StringBuilder();
 for (User user : users) {
 if (builder.length() > 0) builder.append(", ");
 builder.append(user.name);
 }X
 return builder.toString();
 }X Jimmy•McNulty,• Stringer•Bell Jimmy•McNulty,•

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public String names(List users) {
 StringBuilder builder = new StringBuilder();
 for (User user : users) {
 if (builder.length() > 0) builder.append(", ");
 builder.append(user.name);
 }X
 return builder.toString();
 }X Jimmy•McNulty,• Stringer•Bell Jimmy•McNulty,•

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public String names(List users) {
 StringBuilder builder = new StringBuilder();
 for (User user : users) {
 if (builder.length() > 0) builder.append(", ");
 builder.append(user.name);
 }X
 return builder.toString();
 }X Stringer•Bell Jimmy•McNulty,•

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public String names(List users) {
 StringBuilder builder = new StringBuilder();
 for (User user : users) {
 if (builder.length() > 0) builder.append(", ");
 builder.append(user.name);
 }X
 return builder.toString();
 }X Stringer•Bell Jimmy•McNulty,•

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public String names(List users) {
 StringBuilder builder = new StringBuilder();
 for (User user : users) {
 if (builder.length() > 0) builder.append(", ");
 builder.append(user.name);
 }X
 return builder.toString();
 }X Stringer•Bell Jimmy•McNulty,•

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public String names(List users) {
 StringBuilder builder = new StringBuilder();
 for (User user : users) {
 if (builder.length() > 0) builder.append(", ");
 builder.append(user.name);
 }X
 return builder.toString();
 }X Jimmy•McNulty,•Stringer•Bell

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public String names(List users) {
 StringBuilder builder = new StringBuilder();
 for (User user : users) {
 if (builder.length() > 0) builder.append(", ");
 builder.append(user.name);
 }X
 return builder.toString();
 }X Jimmy•McNulty,•Stringer•Bell

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public String names(List users) {
 StringBuilder builder = new StringBuilder();
 for (User user : users) {
 if (builder.length() > 0) builder.append(", ");
 builder.append(user.name);
 }X
 return builder.toString();
 }X Jimmy•McNulty,•Stringer•Bell

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public String names(List users) {
 StringBuilder builder = new StringBuilder();
 for (User user : users) {
 if (builder.length() > 0) builder.append(", ");
 builder.append(user.name);
 }X
 return builder.toString();
 }X Jimmy•McNulty,•Stringer•Bell Jimmy•McNulty,•Stringer•Bell,•

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public String names(List users) {
 StringBuilder builder = new StringBuilder();
 for (User user : users) {
 if (builder.length() > 0) builder.append(", ");
 builder.append(user.name);
 }X
 return builder.toString();
 }X Jimmy•McNulty,•Stringer•Bell,• Jimmy•McNulty,•Stringer•Bell,•

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public String names(List users) {
 StringBuilder builder = new StringBuilder();
 for (User user : users) {
 if (builder.length() > 0) builder.append(", ");
 builder.append(user.name);
 }X
 return builder.toString();
 }X Jimmy•McNulty,•Stringer•Bell,• Bunk•Moreland Jimmy•McNulty,•Stringer•Bell,•

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public String names(List users) {
 StringBuilder builder = new StringBuilder();
 for (User user : users) {
 if (builder.length() > 0) builder.append(", ");
 builder.append(user.name);
 }X
 return builder.toString();
 }X Jimmy•McNulty,•Stringer•Bell,• Bunk•Moreland Jimmy•McNulty,•Stringer•Bell,•

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public String names(List users) {
 StringBuilder builder = new StringBuilder();
 for (User user : users) {
 if (builder.length() > 0) builder.append(", ");
 builder.append(user.name);
 }X
 return builder.toString();
 }X Jimmy•McNulty,•Stringer•Bell,• Bunk•Moreland Jimmy•McNulty,•Stringer•Bell,•

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public String names(List users) {
 StringBuilder builder = new StringBuilder();
 for (User user : users) {
 if (builder.length() > 0) builder.append(", ");
 builder.append(user.name);
 }X
 return builder.toString();
 }X Bunk•Moreland Jimmy•McNulty,•Stringer•Bell,•

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public String names(List users) {
 StringBuilder builder = new StringBuilder();
 for (User user : users) {
 if (builder.length() > 0) builder.append(", ");
 builder.append(user.name);
 }X
 return builder.toString();
 }X Bunk•Moreland Jimmy•McNulty,•Stringer•Bell,•

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public String names(List users) {
 StringBuilder builder = new StringBuilder();
 for (User user : users) {
 if (builder.length() > 0) builder.append(", ");
 builder.append(user.name);
 }X
 return builder.toString();
 }X Bunk•Moreland Jimmy•McNulty,•Stringer•Bell,•

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public String names(List users) {
 StringBuilder builder = new StringBuilder();
 for (User user : users) {
 if (builder.length() > 0) builder.append(", ");
 builder.append(user.name);
 }X
 return builder.toString();
 }X Jimmy•McNulty,•Stringer•Bell,•Bunk•Moreland

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public String names(List users) {
 StringBuilder builder = new StringBuilder();
 for (User user : users) {
 if (builder.length() > 0) builder.append(", ");
 builder.append(user.name);
 }X
 return builder.toString();
 }X Jimmy•McNulty,•Stringer•Bell,•Bunk•Moreland

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public String names(List users) {
 StringBuilder builder = new StringBuilder();
 for (User user : users) {
 if (builder.length() > 0) builder.append(", ");
 builder.append(user.name);
 }X
 return builder.toString();
 }X Jimmy•McNulty,•Stringer•Bell,•Bunk•Moreland

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public String names(List users) {
 StringBuilder builder = new StringBuilder();
 for (User user : users) {
 if (builder.length() > 0) builder.append(", ");
 builder.append(user.name);
 }X
 return builder.toString();
 }X Jimmy•McNulty,•Stringer•Bell,•Bunk•Moreland Jimmy•McNulty,•Stringer•Bell,•Bunk•Moreland,•

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public String names(List users) {
 StringBuilder builder = new StringBuilder();
 for (User user : users) {
 if (builder.length() > 0) builder.append(", ");
 builder.append(user.name);
 }X
 return builder.toString();
 }X Jimmy•McNulty,•Stringer•Bell,•Bunk•Moreland,•

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public String names(List users) {
 StringBuilder builder = new StringBuilder();
 for (User user : users) {
 if (builder.length() > 0) builder.append(", ");
 builder.append(user.name);
 }X
 return builder.toString();
 }X Jimmy•McNulty,•Stringer•Bell,•Bunk•Moreland,• Jimmy•McNulty,•Stringer•Bell,•Bunk•Moreland,•D'Angelo•Barksdale

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Jimmy•McNulty,•Stringer•Bell,•Bunk•Moreland,•D'Angelo•Barksdale public String names(List users) {
 StringBuilder builder = new StringBuilder();
 for (User user : users) {
 if (builder.length() > 0) builder.append(", ");
 builder.append(user.name);
 }X
 return builder.toString();
 }X

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public String names(List users) {
 StringBuilder builder = new StringBuilder();
 for (User user : users) {
 if (builder.length() > 0) builder.append(", ");
 builder.append(user.name);
 }X
 return builder.toString();
 }X

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public String names(List users) {
 int avg = 17; // Determined by exact science.
 StringBuilder builder = new StringBuilder(avg * users.size());
 for (User user : users) {
 if (builder.length() > 0) builder.append(", ");
 builder.append(user.name);
 }X
 return builder.toString();
 }X

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public String names(List users) {
 int avg = 17; // Determined by exact science.
 StringBuilder builder = new StringBuilder(avg * users.size());
 for (User user : users) {
 if (builder.length() > 0) builder.append(", ");
 builder.append(user.name);
 }X
 return builder.toString();
 }X

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for (int x = 0; x < valueCount; x++) {
 cleanFiles[x] = new File(directory, key + "." + x);
 dirtyFiles[x] = new File(directory, key + "." + x + ".tmp");
 }X

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for (int x = 0; x < valueCount; x++) {
 StringBuilder b1 = new StringBuilder();
 b1.append(key);
 b1.append(".");
 b1.append(x);
 cleanFiles[x] = new File(directory, b1.toString());
 StringBuilder b2 = new StringBuilder();
 b2.append(key);
 b2.append(".");
 b2.append(x);
 b2.append(".tmp");
 dirtyFiles[x] = new File(directory, b2.toString());
 }X

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for (int x = 0; x < valueCount; x++) {
 StringBuilder b1 = new StringBuilder();
 b1.append(key);
 b1.append(".");
 b1.append(x);
 cleanFiles[x] = new File(directory, b1.toString());
 StringBuilder b2 = new StringBuilder();
 b2.append(key);
 b2.append(".");
 b2.append(x);
 b2.append(".tmp");
 dirtyFiles[x] = new File(directory, b2.toString());
 }X

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for (int x = 0; x < valueCount; x++) {
 StringBuilder b = new StringBuilder();
 b.append(key);
 b.append(".");
 b.append(x);
 cleanFiles[x] = new File(directory, b.toString());
 b.append(".tmp");
 dirtyFiles[x] = new File(directory, b.toString());
 }X

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for (int x = 0; x < valueCount; x++) {
 StringBuilder b = new StringBuilder();
 b.append(key);
 b.append(".");
 b.append(x);
 cleanFiles[x] = new File(directory, b.toString());
 b.append(".tmp");
 dirtyFiles[x] = new File(directory, b.toString());
 }X

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StringBuilder b = new StringBuilder();
 b.append(key);
 b.append("."); for (int x = 0; x < valueCount; x++) {
 b.append(x);
 cleanFiles[x] = new File(directory, b.toString());
 b.append(".tmp");
 dirtyFiles[x] = new File(directory, b.toString());
 }X

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StringBuilder b = new StringBuilder();
 b.append(key);
 b.append("."); for (int x = 0; x < valueCount; x++) {
 b.append(x);
 cleanFiles[x] = new File(directory, b.toString());
 b.append(".tmp");
 dirtyFiles[x] = new File(directory, b.toString());
 }X

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StringBuilder b = new StringBuilder();
 b.append(key);
 b.append("."); int truncateTo = b.length(); for (int x = 0; x < valueCount; x++) {
 b.append(x);
 cleanFiles[x] = new File(directory, b.toString());
 b.append(".tmp");
 dirtyFiles[x] = new File(directory, b.toString());
 }X

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StringBuilder b = new StringBuilder();
 b.append(key);
 b.append("."); int truncateTo = b.length(); for (int x = 0; x < valueCount; x++) {
 b.append(x);
 cleanFiles[x] = new File(directory, b.toString());
 b.append(".tmp");
 dirtyFiles[x] = new File(directory, b.toString());
 }X

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StringBuilder b = new StringBuilder();
 b.append(key);
 b.append("."); int truncateTo = b.length(); for (int x = 0; x < valueCount; x++) {
 b.append(x);
 cleanFiles[x] = new File(directory, b.toString());
 b.append(".tmp");
 dirtyFiles[x] = new File(directory, b.toString()); b.setLength(truncateTo);
 }X

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StringBuilder b = new StringBuilder();
 b.append(key);
 b.append("."); int truncateTo = b.length(); for (int x = 0; x < valueCount; x++) {
 b.append(x);
 cleanFiles[x] = new File(directory, b.toString());
 b.append(".tmp");
 dirtyFiles[x] = new File(directory, b.toString()); b.setLength(truncateTo);
 }X

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StringBuilder b = new StringBuilder(key.length() + 6);
 b.append(key);
 b.append("."); int truncateTo = b.length(); for (int x = 0; x < valueCount; x++) {
 b.append(x);
 cleanFiles[x] = new File(directory, b.toString());
 b.append(".tmp");
 dirtyFiles[x] = new File(directory, b.toString()); b.setLength(truncateTo);
 }X

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StringBuilder b = new StringBuilder(key.length() + 6);
 b.append(key);
 b.append("."); int truncateTo = b.length(); for (int x = 0; x < valueCount; x++) {
 b.append(x);
 cleanFiles[x] = new File(directory, b.toString());
 b.append(".tmp");
 dirtyFiles[x] = new File(directory, b.toString()); b.setLength(truncateTo);
 }X

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StringBuilder b = new StringBuilder(key);
 b.append("."); int truncateTo = b.length(); for (int x = 0; x < valueCount; x++) {
 b.append(x);
 cleanFiles[x] = new File(directory, b.toString());
 b.append(".tmp");
 dirtyFiles[x] = new File(directory, b.toString()); b.setLength(truncateTo);
 }X

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StringBuilder b = new StringBuilder(key);
 b.append("."); int truncateTo = b.length(); for (int x = 0; x < valueCount; x++) {
 b.append(x);
 cleanFiles[x] = new File(directory, b.toString());
 b.append(".tmp");
 dirtyFiles[x] = new File(directory, b.toString()); b.setLength(truncateTo);
 }X

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StringBuilder b = new StringBuilder(key);
 b.append("."); int truncateTo = b.length(); for (int x = 0; x < valueCount; x++) {
 b.append(x);
 cleanFiles[x] = new File(directory, b.toString());
 b.append(".tmp");
 dirtyFiles[x] = new File(directory, b.toString()); public StringBuilder(String str) Constructs a string builder initialized to the contents of the specified string. The initial capacity of the string builder is 16 plus the length of the string argument.

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StringBuilder b = new StringBuilder(key);
 b.append("."); int truncateTo = b.length(); for (int x = 0; x < valueCount; x++) {
 b.append(x);
 cleanFiles[x] = new File(directory, b.toString());
 b.append(".tmp");
 dirtyFiles[x] = new File(directory, b.toString()); public StringBuilder(String str) Constructs a string builder initialized to the contents of the specified string. The initial capacity of the string builder is 16 plus the length of the string argument.

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StringBuilder b = new StringBuilder(key);
 b.append("."); int truncateTo = b.length(); for (int x = 0; x < valueCount; x++) {
 b.append(x);
 cleanFiles[x] = new File(directory, b.toString());
 b.append(".tmp");
 dirtyFiles[x] = new File(directory, b.toString()); b.setLength(truncateTo);
 }X

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StringBuilder b = new StringBuilder(key).append("."); int truncateTo = b.length(); for (int x = 0; x < valueCount; x++) {
 b.append(x);
 cleanFiles[x] = new File(directory, b.toString()); b.append(".tmp");
 dirtyFiles[x] = new File(directory, b.toString()); b.setLength(truncateTo);
 }X public List names(List users) {
 List names = new ArrayList<>(users.size());
 for (User user : users) {
 names.add(user.name);
 }X
 return unmodifiableList(names);
 }X

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private int headerOffset;
 private int headerTop;
 private int animationHeight;
 
 @Override protected void onCreate(Bundle bundle) {
 super.onCreate(bundle);
 
 setTitle(getResources().getString(R.id.title));
 getWindow().setStatusBarColor(getResources().getColor(R.color.blue));
 
 headerOffset = getResources() .getDimensionPixelSize(R.dimen.header_offset);
 headerTop = getResources() .getDimensionPixelSize(R.dimen.header_top);
 animationHeight = getResources() .getDimensionPixelSize(R.dimen.animation_height);
 }X

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private int headerOffset;
 private int headerTop;
 private int animationHeight;
 
 @Override protected void onCreate(Bundle bundle) {
 super.onCreate(bundle);
 Resources res = getResources();
 
 setTitle(getResources().getString(R.id.title));
 getWindow().setStatusBarColor(getResources().getColor(R.color.blue));
 
 headerOffset = getResources() .getDimensionPixelSize(R.dimen.header_offset);
 headerTop = getResources() .getDimensionPixelSize(R.dimen.header_top);
 animationHeight = getResources() .getDimensionPixelSize(R.dimen.animation_height);
 }X

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private int headerOffset;
 private int headerTop;
 private int animationHeight;
 
 @Override protected void onCreate(Bundle bundle) {
 super.onCreate(bundle);
 Resources res = getResources();
 
 setTitle(res.getString(R.id.title));
 getWindow().setStatusBarColor(res.getColor(R.color.blue));
 
 headerOffset = res.getDimensionPixelSize(R.dimen.header_offset);
 headerTop = res.getDimensionPixelSize(R.dimen.header_top);
 animationHeight = res.getDimensionPixelSize(R.dimen.animation_height);
 }X

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private int headerOffset;
 private int headerTop;
 private int animationHeight;
 
 @Override protected void onCreate(Bundle bundle) {
 super.onCreate(bundle);
 Resources res = getResources();
 
 setTitle(res.getString(R.id.title));
 getWindow().setStatusBarColor(res.getColor(R.color.blue));
 
 headerOffset = res.getDimensionPixelSize(R.dimen.header_offset);
 headerTop = res.getDimensionPixelSize(R.dimen.header_top);
 animationHeight = res.getDimensionPixelSize(R.dimen.animation_height);
 }

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public boolean validIndices(int[] indices, String string) {
 for (int index : indices) {
 if (index < 0 && index >= string.length()) {
 return false;
 }X
 }X
 return true;
 }X

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public boolean validIndices(int[] indices, String string) {
 int len = string.length();
 for (int index : indices) {
 if (index < 0 && index >= len) {
 return false;
 }X
 }X
 return true;
 }X

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public boolean validIndices(int[] indices, String string) {
 int len = string.length();
 for (int index : indices) {
 if (index < 0 && index >= len) {
 return false;
 }X
 }X
 return true;
 }X

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public boolean firstShorterThan(List strings, int max) {
 for (int i = 0; i < strings.size(); i++) {
 if (strings.get(i).length() > max) {
 return i;
 }X
 }X
 return -1;
 }X

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public boolean firstShorterThan(List strings, int max) {
 int i = 0;
 while (i < strings.size()) {X
 if (strings.get(i).length() > max) {Y
 return i;
 }X
 i++;
 }X
 return -1;
 }X

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public boolean firstShorterThan(List strings, int max) {
 int i = 0;
 while (true) {X
 if (!(i < strings.size())) {
 break;
 }Y
 if (strings.get(i).length() > max) {Y
 return i;
 }X
 i++;
 }X
 return -1;
 }X

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public boolean firstShorterThan(List strings, int max) {
 for (int i = 0;ciy max) {
 return i;
 }X
 }X
 return -1;
 }X

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public boolean firstShorterThan(List strings, int max) {
 int size =sstrings.size(); for (int i = 0;ciy< size;xi++) {
 if (strings.get(i).length() > max) {
 return i;
 }X
 }X
 return -1;
 }X

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public boolean firstShorterThan(List strings, int max) {
 int size =sstrings.size(); for (int i = 0;ciy< size;xi++) {
 if (strings.get(i).length() > max) {
 return i;
 }X
 }X
 return -1;
 }X

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public boolean firstShorterThan(List strings, int max) {
 for (int i = 0, size = strings.size();ciy< size;xi++) {
 if (strings.get(i).length() > max) {
 return i;
 }X
 }X
 return -1;
 }X

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public boolean firstShorterThan(List strings, int max) {
 for (int i = 0, size = strings.size();ciy< size;xi++) {
 if (strings.get(i).length() > max) {
 return i;
 }X
 }X
 return -1;
 }X

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No content

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invokestatic static methods

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invokestatic static methods class Test {
 public static void main(String... args) {
 staticMethod();
 } 
 public static void staticMethod() {
 System.out.println("Hello, static method!");
 }
 }

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invokestatic static methods public static void main(java.lang.String...); Code: 0: invokestatic #2 // Method staticMethod:()V 3: return

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invokestatic static methods invokespecial constructors private methods super methods

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invokestatic static methods invokespecial constructors private methods super methods Test(); Code: 0: aload_0 1: invokespecial #1 // Method java/lang/Object."":()V 4: return

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invokestatic static methods invokespecial constructors private methods super methods invokevirtual other class methods

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invokestatic static methods invokespecial constructors private methods super methods invokevirtual other class methods class Test {
 public static void main(String... args) {
 new Test().method();
 }
 
 public void method() {
 System.out.println("Hello, method!");
 }
 }

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invokestatic static methods invokespecial constructors private methods super methods invokevirtual other class methods public static void main(java.lang.String...); Code: ... 8: aload_1 9: invokevirtual #4 // Method method:()V

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invokestatic static methods invokespecial constructors private methods super methods invokevirtual other class methods invokeinterface interface methods

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invokestatic static methods invokespecial constructors private methods super methods invokevirtual other class methods invokeinterface interface methods class Test {
 public static void main(String... args) {
 List names = Arrays.asList("Alice", "Bob", "Eve");
 int size = names.size();
 System.out.println(size);
 }
 }

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invokestatic static methods invokespecial constructors private methods super methods invokevirtual other class methods invokeinterface interface methods public static void main(java.lang.String...); Code: ... 23: aload_1 24: invokeinterface #7, 1 // InterfaceMethod java/util/List.size:()I

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public class MyActivity extends Activity { @Override protected void onCreate(Bundle bundle) {
 super.onCreate(bundle);
 Resources res = getResources(); // ...
 }X @Override public String toString() {
 return "MyActivity";
 }X }X

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public class MyActivity extends Activity { @Override protected void onCreate(Bundle bundle) {
 super.onCreate(bundle);
 Resources res = getResources(); // ...
 }X @Override public String toString() {
 return "MyActivity";
 }X }X Method Address

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public class MyActivity extends Activity { @Override protected void onCreate(Bundle bundle) {
 super.onCreate(bundle);
 Resources res = getResources(); // ...
 }X @Override public String toString() {
 return "MyActivity";
 }X }X Method Address MyActivity Activity ContextThemeWrapper Context Object

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public class MyActivity extends Activity { @Override protected void onCreate(Bundle bundle) {
 super.onCreate(bundle);
 Resources res = getResources(); // ...
 }X @Override public String toString() {
 return "MyActivity";
 }X }X Method Address MyActivity Activity ContextThemeWrapper Context Object

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public class MyActivity extends Activity { @Override protected void onCreate(Bundle bundle) {
 super.onCreate(bundle);
 Resources res = getResources(); // ...
 }X @Override public String toString() {
 return "MyActivity";
 }X }X Method Address Object.toString 101 MyActivity Activity ContextThemeWrapper Context Object

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public class MyActivity extends Activity { @Override protected void onCreate(Bundle bundle) {
 super.onCreate(bundle);
 Resources res = getResources(); // ...
 }X @Override public String toString() {
 return "MyActivity";
 }X }X Method Address Object.toString 101 Object.hashCode 102 MyActivity Activity ContextThemeWrapper Context Object

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public class MyActivity extends Activity { @Override protected void onCreate(Bundle bundle) {
 super.onCreate(bundle);
 Resources res = getResources(); // ...
 }X @Override public String toString() {
 return "MyActivity";
 }X }X Method Address Object.toString 101 Object.hashCode 102 ... MyActivity Activity ContextThemeWrapper Context Object

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Method Address Object.toString 101 Object.hashCode 102 ... public class MyActivity extends Activity { @Override protected void onCreate(Bundle bundle) {
 super.onCreate(bundle);
 Resources res = getResources(); // ...
 }X @Override public String toString() {
 return "MyActivity";
 }X }X MyActivity Activity ContextThemeWrapper Context Object

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Method Address Object.toString 101 Object.hashCode 102 Context.getResources 201 ... public class MyActivity extends Activity { @Override protected void onCreate(Bundle bundle) {
 super.onCreate(bundle);
 Resources res = getResources(); // ...
 }X @Override public String toString() {
 return "MyActivity";
 }X }X MyActivity Activity ContextThemeWrapper Context Object

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public class MyActivity extends Activity { @Override protected void onCreate(Bundle bundle) {
 super.onCreate(bundle);
 Resources res = getResources(); // ...
 }X @Override public String toString() {
 return "MyActivity";
 }X }X MyActivity Activity ContextThemeWrapper Context Object Method Address Object.toString 101 Object.hashCode 102 Context.getResources 201 ...

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Method Address Object.toString 101 Object.hashCode 102 ContextTW.getResources 301 ... public class MyActivity extends Activity { @Override protected void onCreate(Bundle bundle) {
 super.onCreate(bundle);
 Resources res = getResources(); // ...
 }X @Override public String toString() {
 return "MyActivity";
 }X }X MyActivity Activity ContextThemeWrapper Context Object

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public class MyActivity extends Activity { @Override protected void onCreate(Bundle bundle) {
 super.onCreate(bundle);
 Resources res = getResources(); // ...
 }X @Override public String toString() {
 return "MyActivity";
 }X }X Method Address Object.toString 101 Object.hashCode 102 ContextTW.getResources 301 ... MyActivity Activity ContextThemeWrapper Context Object

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public class MyActivity extends Activity { @Override protected void onCreate(Bundle bundle) {
 super.onCreate(bundle);
 Resources res = getResources(); // ...
 }X @Override public String toString() {
 return "MyActivity";
 }X }X MyActivity Activity ContextThemeWrapper Context Object Method Address Object.toString 101 Object.hashCode 102 ContextTW.getResources 301 ...

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public class MyActivity extends Activity { @Override protected void onCreate(Bundle bundle) {
 super.onCreate(bundle);
 Resources res = getResources(); // ...
 }X @Override public String toString() {
 return "MyActivity";
 }X }X MyActivity Activity ContextThemeWrapper Context Object Method Address MyActivity.toString 501 Object.hashCode 102 ContextTW.getResources 301 ...

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public class MyActivity extends Activity { @Override protected void onCreate(Bundle bundle) {
 super.onCreate(bundle);
 Resources res = getResources(); // ...
 }X @Override public String toString() {
 return "MyActivity";
 }X }X Method Address MyActivity.toString 501 Object.hashCode 102 ContextTW.getResources 301 ...

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public class MyActivity extends Activity { @Override protected void onCreate(Bundle bundle) {
 super.onCreate(bundle);
 Resources res = getResources(); // ...
 }X @Override public String toString() {
 return "MyActivity";
 }X }X Method Address MyActivity.toString 501 Object.hashCode 102 ContextTW.getResources 301 ... getResources();

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public class MyActivity extends Activity { @Override protected void onCreate(Bundle bundle) {
 super.onCreate(bundle);
 Resources res = getResources(); // ...
 }X @Override public String toString() {
 return "MyActivity";
 }X }X Method Address MyActivity.toString 501 Object.hashCode 102 ContextTW.getResources 301 ... getResources(); Method table lookup

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public class MyActivity extends Activity { @Override protected void onCreate(Bundle bundle) {
 super.onCreate(bundle);
 Resources res = getResources(); // ...
 }X @Override public String toString() {
 return "MyActivity";
 }X }X Method Address MyActivity.toString 501 Object.hashCode 102 ContextTW.getResources 301 ... getResources(); Method table lookup Jump

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public class MyActivity extends Activity { @Override protected void onCreate(Bundle bundle) {
 super.onCreate(bundle);
 Resources res = getResources(); // ...
 }X @Override public String toString() {
 return "MyActivity";
 }X }X Method Address MyActivity.toString 501 Object.hashCode 102 ContextTW.getResources 301 ... getResources(); getResources(); getResources(); getResources(); getResources(); Method table lookup Jump Method table lookup Jump Method table lookup Jump Method table lookup Jump Method table lookup Jump

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public boolean firstShorterThan(List strings, int max) {
 for (int i = 0; i < strings.size(); i++) {
 if (strings.get(i).length() > max) {
 return i;
 }X
 }X
 return -1;
 }X 
 strings.size()

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public boolean firstShorterThan(List strings, int max) {
 for (int i = 0; i < strings.size(); i++) {
 if (strings.get(i).length() > max) {
 return i;
 }X
 }X
 return -1;
 }X strings.size()

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public boolean firstShorterThan(List strings, int max) {
 for (int i = 0; i < strings.size(); i++) {
 if (strings.get(i).length() > max) {
 return i;
 }X
 }X
 return -1;
 }X strings.size() Class lookup

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public boolean firstShorterThan(List strings, int max) {
 for (int i = 0; i < strings.size(); i++) {
 if (strings.get(i).length() > max) {
 return i;
 }X
 }X
 return -1;
 }X strings.size() Method table lookup Jump Class lookup

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What about JIT & AOT compilers?

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Resources res = getResources();

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Resources res = getResources(); public Resources getResources() {
 return mResources;
 }X private Resources mResources;

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Resources res = mResources; private Resources mResources;

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Resources res = mResources; private Resources mResources; mResources

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Resources res = mResources; private Resources mResources; mResources Memory lookup

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Resources res = mResources; private Resources mResources; mResources Memory lookup Copy to local

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Resources res = mResources; private Resources mResources; mResources Memory lookup Copy to local mResources mResources mResources mResources

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Resources res = mResources; private Resources mResources; mResources Memory lookup Copy to local mResources mResources mResources mResources Memory lookup Copy to local Memory lookup Copy to local Memory lookup Copy to local Memory lookup Copy to local

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for (int i = 0; i < strings.size(); i++)

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for (int i = 0; i < strings.size(); i++) @Override public int size() {
 return ;
 } int size; 
 size

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for (int i = 0; ix< strings. ;yi++) int size; size

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for (int i = 0; ix< strings.size;yi++) int size; size

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for (int i = 0; ix< strings.size;yi++) int size; size Memory lookup Copy to local

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for (int i = 0; ix< strings.size;yi++) int size; size Memory lookup Copy to local size Memory lookup Copy to local size Memory lookup Copy to local size Memory lookup Copy to local size Memory lookup Copy to local size Memory lookup Copy to local size Memory lookup Copy to local size Memory lookup Copy to local size Memory lookup Copy to local size Memory lookup Copy to local size Memory lookup Copy to local size Memory lookup Copy to local size Memory lookup Copy to local size Memory lookup Copy to local size Memory lookup Copy to local size Memory lookup Copy to local size Memory lookup Copy to local size Memory lookup Copy to local size Memory lookup Copy to local size Memory lookup Copy to local size Memory lookup Copy to local size Memory lookup Copy to local size Memory lookup Copy to local size Memory lookup Copy to local size Memory lookup Copy to local size Memory lookup Copy to local size Memory lookup Copy to local size Memory lookup Copy to local size Memory lookup Copy to local size Memory lookup Copy to local size Memory lookup Copy to local size Memory lookup Copy to local size Memory lookup Copy to local size Memory lookup Copy to local size Memory lookup Copy to local size Memory lookup Copy to local size Memory lookup Copy to local size Memory lookup Copy to local size Memory lookup Copy to local size Memory lookup Copy to local size Memory lookup Copy to local size Memory lookup Copy to local size Memory lookup Copy to local size Memory lookup Copy to local size Memory lookup Copy to local size Memory lookup Copy to local Memory lookup Copy to local size Memory lookup Copy to local size Memory lookup Copy to local size Memory lookup Copy to local size Memory lookup Copy to local size Memory lookup Copy to local size Memory lookup Copy to local size Memory lookup Copy size Memory lookup ookup Copy to local size Memory

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for (int i = 0; ix< strings.size;yi++) int size;

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for (int i = 0, size = strings.size; ix< size;yi++) int size;

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for (int i = 0, size = strings.size; ix< size;yi++) int size; Memory lookup Copy to local size

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StringBuilder b = new StringBuilder(key).append("."); int truncateTo = b.length(); for (int x = 0; x < valueCount; x++) {
 b.append(x);
 cleanFiles[x] = new File(directory, b.toString()); b.append(".tmp");
 dirtyFiles[x] = new File(directory, b.toString()); b.setLength(truncateTo);
 }X public List names(List users) {
 List names = new ArrayList<>(users.size());
 for (User user : users) {
 names.add(user.name);
 }X
 return unmodifiableList(names);
 }X

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public List names(List users) {
 List names = new ArrayList<>(users.size());
 for (User user : users) {
 names.add(user.name);
 }X
 return unmodifiableList(names);
 }X

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public List names(List users) {
 List names = new ArrayList<>(users.size());
 for (Iterator iter = users.iterator(); iter.hasNext(); ) {
 User user = iter.next();
 names.add(user.name);
 }X
 return unmodifiableList(names);
 }X

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public List names(List users) {
 List names = new ArrayList<>(users.size());
 for (Iterator iter = users.iterator(); iter.hasNext(); ) {
 User user = iter.next();
 names.add(user.name);
 }X
 return unmodifiableList(names);
 }X

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public List names(List users) {
 List names = new ArrayList<>(users.size());
 for (Iterator iter = users.iterator(); iter.hasNext(); ) {
 User user = iter.next();
 names.add(user.name);
 }X
 return unmodifiableList(names);
 }X

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public List names(List users) {
 List names = new ArrayList<>(users.size());
 for (Iterator iter = users.iterator(); iter.hasNext(); ) {
 User user = iter.next();
 names.add(user.name);
 }X
 return unmodifiableList(names);
 }X

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public List names(List users) {
 List names = new ArrayList<>(users.size());
 for (Iterator iter = users.iterator(); iter.hasNext(); ) {
 User user = iter.next();
 names.add(user.name);
 }X
 return unmodifiableList(names);
 }X

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public List names(List users) {
 List names = new ArrayList<>(users.size());
 for (Iterator iter = users.iterator(); iter.hasNext(); ) {
 User user = iter.next();
 names.add(user.name);
 }X
 return unmodifiableList(names);
 }X

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public List names(List users) {
 List names = new ArrayList<>(users.size());
 for (int x = 0, size = users.size(); x < size; x++) {
 User user = users.get(x);
 names.add(user.name);
 }X
 return unmodifiableList(names);
 }X

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public List names(List users) {
 List names = new ArrayList<>(users.size());
 for (int x = 0, size = users.size(); x < size; x++) {
 User user = users.get(x);
 names.add(user.name);
 }X
 return unmodifiableList(names);
 }X

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StringBuilder b = new StringBuilder(key).append("."); int truncateTo = b.length(); for (int x = 0; x < valueCount; x++) {
 b.append(x);
 cleanFiles[x] = new File(directory, b.toString()); b.append(".tmp");
 dirtyFiles[x] = new File(directory, b.toString()); b.setLength(truncateTo);
 }X

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int valueCount = this.valueCount; File directory = this.directory; File[] cleanFiles = this.cleanFiles; File[] dirtyFiles = this.dirtyFiles; StringBuilder b = new StringBuilder(key).append("."); int truncateTo = b.length(); for (int x = 0; x < valueCount; x++) {
 b.append(x);
 cleanFiles[x] = new File(directory, b.toString()); b.append(".tmp");
 dirtyFiles[x] = new File(directory, b.toString()); b.setLength(truncateTo);
 }X

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StringBuilder b = new StringBuilder(key).append("."); int truncateTo = b.length(); for (int x = 0; x < valueCount; x++) {
 b.append(x);
 cleanFiles[x] = new File(directory, b.toString()); b.append(".tmp");
 dirtyFiles[x] = new File(directory, b.toString()); b.setLength(truncateTo);
 }X

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What else? • Polymorphic virtual method calls • Monomorphic vs. bimorphic vs. megamorphic • Concurrency implications & locks • Read/write when lock, act out of lock • synchronized vs. concurrent lock types

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