Stream流提取对象集合的id

public class StreamTest {

private Integer id;

private Integer age;

private String name;



public StreamTest() {

}



public StreamTest(Integer id, Integer age, String name) {

    this.id = id;

    this.age = age;

    this.name = name;

}

todo 省略 getting、setting方法

}

测试

public static void main(String[] args) {

    List<StreamTest> list = new ArrayList<>();

    StreamTest object  = new StreamTest(1,25,"尚佳鹏");

    StreamTest object1 = new StreamTest(2,24,"标哥");

    StreamTest object2 = new StreamTest(3,25,"李鹏");

    StreamTest object3 = new StreamTest(4,18,"姚孟");

    list.add(object);

    list.add(object1);

    list.add(object2);

    list.add(object3);

    List<Integer> ids = list.stream().map(StreamTest::getId).collect(Collectors.toList());

    System.err.println("所有的id : "+ids);

    List<Integer> ages = list.stream().map(StreamTest::getAge).collect(Collectors.toList());

    System.out.println("未去重的年龄 : "+ages);

    List<Integer> agess = list.stream().map(StreamTest::getAge).distinct().collect(Collectors.toList());

    System.err.println("已去重的年龄 : "+agess);

}

控制台输出结果

所有的id : [1, 2, 3, 4]

未去重的年龄 : [25, 24, 25, 18]

已去重的年龄 : [25, 24, 18]