【Java】Lambda表达式(三)

常用 Lambda表达式

1、遍历

final List<String> list = Arrays.asList("zhangsan", "lisi", "wangwu", "lishan");
list.forEach(System.out::println)；;

2、排序

final List<String> list = Arrays.asList("zhangsan", "lisi", "wangwu", "lishan");
// 第一种
//        list.sort(String::compareTo);
// 第二种
//        Collections.sort(list, String::compareTo);
// 第三种
Collections.sort(list, (o1, o2) -> o1.compareTo(o2));
list.forEach(System.err::println);

3、过滤

final List<String> list = Arrays.asList("zhangsan", "lisi", "wangwu", "lishan");
List<String> list1 = list.stream().filter(s -> s.startsWith("l")).collect(toList());
list1.forEach(System.out::println);

4、映射

final List<String> list = Arrays.asList("zhangsan", "lisi", "wangwu", "lishan");
List<Integer> collect = list.stream().map(String::length).collect(toList());
collect.forEach(System.out::println);

5、归约

List<Integer> list2 = Arrays.asList(1, 2, 3, 5, 6, 7, 8);
//        Integer sum = list2.stream().reduce(0, (a, b) -> a + b);
Integer sum = list2.stream().reduce(0, (a, b) -> {
            System.out.printf("%d ,%d \n", a, b);
            return a + b;
            });
System.out.println(sum);

6、分组

final List<String> list = Arrays.asList("zhangsan", "lisi", "wangwu", "lishan");
Map<Integer, List<String>> collect = list.stream().collect(groupingBy(String::length));
        collect.forEach((k, v) -> {
            System.out.printf("k=%s,v=%s", k, CollUtil.toList(v));
        });