gistfile1.java

// http://d.hatena.ne.jp/nowokay/20140330#1396177524
import java.util.*;
import java.util.function.*;
import java.util.stream.*;

public class LoopBench2 {
    public static void main(String[] args) {
        List<Integer> list = IntStream.range(0, 100_000).boxed().collect(Collectors.toList());
		array = list.toArray(new Integer[0]);
	  	for (int i = 0; i < 10; i++) {
          bench("index", LoopBench2::index);
          bench("forEach", LoopBench2::forEach);
          bench("stream", LoopBench2::stream);
          bench("intreduce", LoopBench2::intreduce);
          bench("reduce", LoopBench2::reduce);
		  }
    }
    
    static Integer[] array; 
    static Integer forEach(){
        int c = 0;
        for(Integer i : array){
            c += i;
        }
        return c;
    }

    static Integer index(){
        int c = 0;
        for(int i = 0; i < array.length; ++i){
            c += array[i];
        }
        return c;
    }
    static Integer stream(){
        int[] c = {0};
        Arrays.stream(array).forEach(i -> c[0] += i);
        return c[0];
    }
    static Integer reduce(){
        return Arrays.stream(array).collect(Collectors.summingInt(i -> i));
    }
    static Integer intreduce(){
        return Arrays.stream(array).mapToInt(i -> i).sum();
    }
    public static void bench(String name, Supplier<Integer> proc){
        bench(name, 50_000, proc);
    }
    public static void bench(String name, int count, Supplier<Integer> proc){
        for(int i = 0; i < 100; ++i){
            proc.get();
        }
        long s = System.currentTimeMillis();
        for(int i = 0; i < count; ++i){
            proc.get();
        }
        System.out.printf("%s(%d):%dms%n", name, proc.get(), System.currentTimeMillis() - s);
    }
}