测试 for foreach stream 性能

import com.google.common.collect.Lists;
import org.junit.Test;

import java.util.List;
import java.util.stream.Collectors;

/**
 *
 */
public class Demo {

    @Test
    public void test() throws InterruptedException {
//        int size = 5000000;
        int size = 50000000;

        Thread.sleep(1000);

        long t1s = System.currentTimeMillis();
        List<Integer> list1 = Lists.newArrayListWithExpectedSize(size);
        for (int i = 0; i < size; i++) {
            list1.add(i + 1);
        }
        long t1e = System.currentTimeMillis();
        System.out.println("for 循环 耗时:" + (t1e - t1s) + " , size = " + list1.size());


        long t2s = System.currentTimeMillis();
        List<Integer> list2 = Lists.newArrayListWithExpectedSize(size);
        list1.forEach(
                i -> list2.add(i + 1)
        );
        long t2e = System.currentTimeMillis();
        System.out.println("foreach  耗时:" + (t2e - t2s) + " , size = " + list2.size());


        long t3s = System.currentTimeMillis();
        List<Integer> list3 = list1.stream().map(i -> i + 1).collect(Collectors.toList());
        long t3e = System.currentTimeMillis();
        System.out.println("stream  耗时:" + (t3e - t3s) + " , size = " + list3.size());

        Thread.sleep(1000);
    }


}

测试结果：