Tools-stream-中间终止操作

//找到年龄大于22岁的人

List<Person> list = new ArrayList<Person>();
list.add(new Person("小王", 23));
list.add(new Person("小力", 25));
list.add(new Person("小美", 18));
list.add(new Person("小明", 16));

list.stream().filter(e -> e.getAge() > 22).forEach(s -> System.out.println(s));

//获取前2个元素
List<Person> list = new ArrayList<Person>();
list.add(new Person("小王", 23));
list.add(new Person("小力", 25));
list.add(new Person("小美", 18));
list.add(new Person("小明", 16));

list.stream().limit(2).forEach(s-> System.out.println(s));

//跳过前2个元素
List<Person> list = new ArrayList<Person>();
list.add(new Person("小王", 23));
list.add(new Person("小力", 25));
list.add(new Person("小美", 18));
list.add(new Person("小明", 16));

list.stream().skip(2).forEach(s-> System.out.println(s));

//去重复，把小明去重复   需要重写hashCode 和 equals 方法
List<Person> list = new ArrayList<Person>();
list.add(new Person("小王", 23));
list.add(new Person("小力", 25));
list.add(new Person("小美", 18));
list.add(new Person("小明", 16));
list.add(new Person("小明", 16));

list.stream().distinct().forEach(s-> System.out.println(s));

// 按照年龄来顺序排列
List<Person> list = new ArrayList<Person>();
list.add(new Person("小王", 23));
list.add(new Person("小力", 25));
list.add(new Person("小美", 18));
list.add(new Person("小明", 16));
list.add(new Person("小明", 16));

list.stream().sorted((s1,s2)->Double.compare(s1.getAge(),s2.getAge())).forEach(s -> System.out.println(s));

// 获取到姓名 转换为 map
List<Person> list = new ArrayList<Person>();
list.add(new Person("小王", 23));
list.add(new Person("小力", 25));
list.add(new Person("小美", 18));
list.add(new Person("小明", 16));
list.add(new Person("小明", 16));

list.stream().map( e -> e.getName() ).forEach(s -> System.out.println(s));

// 使用 parallelStream 来多线程效率   

//  parallelStream  多线的效率比 stream 的效率高
List<Person> list = new ArrayList<Person>();
list.add(new Person("小王", 23));
list.add(new Person("小力", 25));
list.add(new Person("小美", 18));
list.add(new Person("小明", 16));
list.add(new Person("小明", 16));

list.parallelStream().forEach(s -> System.out.println(s));

// 没有调用 forEach 则不会终止流
List<Person> list = new ArrayList<Person>();
list.add(new Person("小王", 23));
list.add(new Person("小力", 25));
list.add(new Person("小美", 18));
list.add(new Person("小明", 16));
list.add(new Person("小明", 16));

list.stream().filter(e->{
    System.out.println("这个地方不调用 forEach 则不会终止流");
    return e.getAge() >22;
}).forEach(System.out::println);

// 获取年龄最小的员工
List<Person> list = new ArrayList<Person>();
list.add(new Person("小王", 23));
list.add(new Person("小力", 25));
list.add(new Person("小美", 18));
list.add(new Person("小明", 16));
list.add(new Person("小明", 16));

Optional<Person> min = list.stream().min((e1, e2) -> Double.compare(e1.getAge(), e2.getAge()));
System.out.println(min.get());

// 获取list的个数
List<Person> list = new ArrayList<Person>();
list.add(new Person("小王", 23));
list.add(new Person("小力", 25));
list.add(new Person("小美", 18));
list.add(new Person("小明", 16));
list.add(new Person("小明", 16));

long count = list.stream().count();
System.out.println(count);

// 获取姓名作为一个集合
List<Person> list = new ArrayList<Person>();
list.add(new Person("小王", 23));
list.add(new Person("小力", 25));
list.add(new Person("小美", 18));
list.add(new Person("小明", 16));
list.add(new Person("小明", 16));

List<String> collect = list.stream().map(e -> e.getName()).collect(Collectors.toList());
collect.stream().forEach(s-> System.out.println(s));