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Don’t Reinvent
The Wheel
Kenju Wagatsuma
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Agenda: ->
❖ 1m : Introduction
❖ 3m : Main part
❖ 1m : Conclusion
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/**
* Introduce Myself
*
* @kenjuwagatsuma
*/
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'me' = {
name : 'Kenju Wagatsuma ( KJ )’,
}
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'me' = {
name : 'Kenju Wagatsuma ( KJ )’,
company : 'Recruit Technologies Co.,LTD.',
}
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'me' = {
name : 'Kenju Wagatsuma ( KJ )’,
company : 'Recruit Technologies Co.,LTD.',
profession : 'Android Development',
}
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'me' = {
name : 'Kenju Wagatsuma ( KJ )’,
company : 'Recruit Technologies Co.,LTD.',
profession : 'Android Development',
favs : {
'Book' : ‘Soft Skills',
'Music' : ‘The Beatles',
'Hobby' : ‘Acoustic Guitar',
'Sport' : 'Rugby'
}
}
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/**
* My Story
*
* @author me
*/
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```java
/**
* Validate user id input from a form
*
* @param String userID
*/
private void validateUserId(String userId) {
// Validate userId
}
```
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```java
private void validateUserId(String userId) {
// Check input field here
if (userId == null || userId.length() == 0) {
return;
}
// Validate userId
}
```
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```java
// Utility class
public static class UtilClass {
public static boolean checkStringInput(String str) {
if (str == null || str.length() == 0) {
return true;
} else {
return false;
}
}
}
// Activity class
public void MainActivity extends Activity {
private void validateUserId(String userId) {
if(UtilClass.checkStringInput(userId)) return;
// Validate userId
// ...
}
}
```
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/**
* @codereview
*
*/
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No content
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No content
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```java
private void validateUserId(String userId) {
// Check input field here
if (userId == null || userId.length() == 0) {
return;
}
// Validate userId
}
```
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```java
private void validateUserId(String userId) {
// Check input field here
if (TextUtils.isEmpty(userId)) {
return;
}
// Validate userId
}
```
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Okay, I’ll look at the
source code, sir…
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```java
/**
* Returns true if the string is null or 0-length.
* @param str the string to be examined
* @return true if str is null or zero length
*/
public static boolean isEmpty(CharSequence str) {
if (str == null || str.length() == 0)
return true;
else
return false;
}
```
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……
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……ʮ͍ͬ͠ΐΜ͚wʯ
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```java
public static boolean checkStringInput(String str) {
if (str == null || str.length() == 0) {
return true;
} else {
return false;
}
}
```
My Code
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```java
public static boolean isEmpty(CharSequence str) {
if (str == null || str.length() == 0)
return true;
else
return false;
}
```
android.TextUtils
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```java
public static boolean checkStringInput(String str) {
if (str == null || str.length() == 0) {
return true;
} else {
return false;
}
}
```
My Code
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```java
public static boolean isEmpty(CharSequence str) {
if (str == null || str.length() == 0)
return true;
else
return false;
}
```
android.TextUtils
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……ʮ͍ͬ͠ΐΜ͚wʯ(࠶)
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/**
* Why TextUtils?
* (not my own code)
*
*/
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#47
ʮϥΠϒϥϦʔΛΓɺ
ϥΠϒϥϦʔΛ͏ʯ
“Effective Java” 2nd Edition
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#47
ʮϥΠϒϥϦʔΛΓɺϥΠϒϥϦʔΛ͏ʯ
ར̍
❖ ඪ४ϥΠϒϥϦΛ༻͢Δ͜ͱͰɺͦΕΛॻ͍
ͨઐՈͷࣝͱɺͦΕΛ͋ͳͨΑΓલʹ༻
ͨ͠ਓʑͷܦݧΛར༻͢Δ͜ͱʹͳΓ·͢ɻ
“Effective Java” 2nd Edition
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#47
ʮϥΠϒϥϦʔΛΓɺϥΠϒϥϦʔΛ͏ʯ
ར̎
❖ ࣗͷ՝ʹগ͔͠Γؔ࿈͍ͯ͠Δʹର
͢ΔͨΓతͳղܾࡦΛॻ͘͜ͱͰɺ࣌ؒΛແ
ବʹ͢Δඞཁ͕ແ͍ɻ
“Effective Java” 2nd Edition
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#47
ʮϥΠϒϥϦʔΛΓɺϥΠϒϥϦʔΛ͏ʯ
ར̏
❖ ࣗͰԿ͠ͳͯ͘ɺଟ͘ͷਓʹΑͬͯ܁
Γฦ͠ॻ͖͞ΕΔίʔυɺ࣌ؒͱڞʹύ
ϑΥʔϚϯε͕վળ͞ΕΔʢࣗͷίʔυͰͦ
͏͍͔ͳ͍ʣɻ
“Effective Java” 2nd Edition
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/**
* So what?
*
* @return Conclusion
*/
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#47
ʮϥΠϒϥϦʔΛΓɺϥΠϒϥϦʔΛ͏ʯ
For All Beginners,
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1. Know Android Library
2. Use Library methods
3. See & Understand source codes
3 Steps for Learning,
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/**
* Appendix
*
*/
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❖ android.text.format.DateUtils
❖ android.text.format.Formatter
❖ android.text.TextUtils
❖ android.text.util.Linkify
❖ android.util.Pair
❖ android.util.SparseArray
❖ android.util.Log
❖ android.util.LruCache
❖ android.graphics.Color
❖ android.media.ThumbnailUtils
android.*
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android.text.TextUtils
```java
/**
* ༩͑ΒΕͨจࣈྻ͕͔ͯ͢Ͳ͏͔Λఆ
*/
public static boolean isDigitsOnly(CharSequence str) {
final int len = str.length();
for (int i = 0; i< len; i++) {
if (!Character.isDigit(str.charAt(i)) {
return false;
}
}
return true;
}
```
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android.text.TextUtils
```java
/**
* HTMLΤϯίʔυ
*/
public static boolean htmlEncode(String s) {
StringBuilder sb = new StringBuilder();
char c;
for (int i = 0; i < s.length(); i++) {
c = s.charAt(i);
switch(c) {
case '<':
sb.append("<");
break;
//...ͦͷଞͷΤϯίʔυ͖͢จࣈ
default:
sb.append(c);
}
}
return sb.toString();
}
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android.text.TextUtils
```java
/**
* trim()Ͱআ͞ΕۭͨനͷΛฦ͠·͢
*/
public static int getTrimmedLength(CharSequence s) {
int len = s.length();
int start = 0;
while (start < len && s.charAt(start) <= ' ') {
start++;
}
int end = 0;
while (end > start && s.charAt(end - 1) <= ' ') {
end--;
}
return end - start;
}
```
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android.database.DatabaseUtils
```java
/**
* WHERE۟࡞ͷϔϧύʔϝιου
*/
public static String concatenateWhere(String a, String b) {
if (TextUtils.isEmpty(a)) {
return b;
}
if (TextUtils.isEmpty(b)) {
return a;
}
return "(" + a + ") AND (" + b + ")";
}
```
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android.database.DatabaseUtils
```java
/**
* CursorͷதΛग़ྗ͢Δσόοά༻ϝιου
*/
public static void dumpCursor(Cursor cursor) {
dumpCursor(cursor, System.out);
}
public static void dumpCursor(Cursor cursor, PrintStream stream) {
stream.println(">>>>> Dumping cursor " + cursor);
if (cursor != null) {
int startPos = cursor.getPosition();
cursor.moveToPosition(-1);
while (cursor.moveToNext()) {
dumpCurrentRow(cursor, stream);
}
cursor.moveToPosition(startPos);
}
stream.println("<<<<<");
}
```
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android.database.DatabaseUtils
```java
/**
* CursorͷݱࡏͷߦΛग़ྗ͢Δ
*/
public static void dumpCurrentRow(Cursor cursor, PrintStream stream) {
String[] cols = cursor.getColumnNames();
stream.println("" + cursor.getPosition() + " {");
int length = cols.length;
for (int i = 0; i < length; i++) {
String value;
try {
value = cursor.getString(i);
} catch (SQLiteException e) {
value = "";
}
stream.println(" " + cols[i] + '=' + value);
}
stream.println("}");
}
```
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/**
* And Much More!
*
* Happy Coding!
*
*/