Slide 3
Slide 3 text
Concise Code
…
private static boolean isInteger(String s) {
return s.matches("-?\\d+");
}
private static int partitionPoint(List list, Predicate predicate) {
for (int i = 0; i < list.size(); i++) {
if (!predicate.test(list.get(i))) {
return i;
}
}
return list.size();
}
}
// 10 times slower
import java.util.Arrays;
import java.util.Comparator;
import java.util.List;
import java.util.Map;
import java.util.function.Predicate;
import java.util.stream.Collectors;
public class SortNumericStrings {
private static final Map WORD_NUMBERS = Map.of(
"ZERO", 0, "ONE", 1, "TWO", 2, /* ...add more... */ "TEN", 10
);
public static void main(String[] args) {
List nums = Arrays.asList("222", "ZERO", "4", "33", "PI", "TWO");
nums.sort(Comparator.comparing(SortNumericStrings::isInteger));
int pp = partitionPoint(nums, s -> !isInteger(s));
nums.subList(0, pp).sort(Comparator.reverseOrder());
nums.subList(pp, nums.size()).sort(Comparator.comparingInt(Integer::parseInt));
if (!nums.equals(List.of("ZERO", "TWO", "PI", "4", "33", "222"))) {
throw new AssertionError("Sort mismatch: " + nums);
}
List result = nums.stream().map(s -> {
if (isInteger(s)) {
return Integer.parseInt(s);
} else if ("PI".equals(s)) {
return java.lang.Math.PI;
} else if ("E".equals(s)) {
return java.lang.Math.E;
} else if (WORD_NUMBERS.containsKey(s)) {
return WORD_NUMBERS.get(s);
} else {
throw new IllegalArgumentException("Unknown literal: " + s);
}
}).collect(Collectors.toList());
List expected = List.of(0, 2, Math.PI, 4, 33, 222);
if (!result.equals(expected)) {
throw new AssertionError("Transformation mismatch: " + result);
}
}
…
var nums = ['222', 'ZERO', '4', '33', 'PI', 'TWO']
assert nums.toSorted() == ['222', '33', '4', 'PI',
'TWO', 'ZERO']
nums.sort(String::isInteger)
var pp = nums.partitionPoint{ !it.integer }
nums.sort(0.. it.toInteger()
case ['PI', 'E'] -> Math."$it"
default -> BigInteger."$it"
}
} == [0, 2, 3.141592653589793, 4, 33, 222]