java1.8中Lambda表达式reduce聚合测试例子

public class LambdaTest {

public static void main(String[] args) {
// 相当于foreach遍历操作结果值
Integer out = Stream.of(10, 5, 3, 2, 1, 0).reduce((result, item) -> {
if (item >= 3) {
result = result + item;
}
return result;
}).get();
System.out.println(out);

// 相当于给定初始结果值，foreach遍历操作结果值
Integer sum = Stream.of(10, 5, 3, 2, 1, 0).reduce(9, LambdaTest::sumTest);
System.out.println(sum);

//相当于给定初始结果值，两个foreach遍历操作结果值
int str = Stream.of(1,2,3).parallel().reduce(1, (result, item) -> {
return result + item;
} , (result, item) -> {
//注：只有并行parallel下才会进入此方法
return result + item ;
});
System.out.println(str);
}

//替换Integer::sum测试
public static Integer sumTest(int a1, int a2) {
return a1 + a2;
}

}