JDK1.8--体验Stream表达式，从一个对象集合中获取每一个对象的某一个值返回新集合

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开发工具eclipse

package com.echo.demo;

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

public class GetStreamLong {
	
	public static void main(String[] args) {
		
		A a = new A();
		a.setId(1);
		a.setAge(22);
		a.setName("a");
		
		A a1 = new A();
		a1.setId(2);
		a1.setAge(22);
		a1.setName("a1");
		
		A a2 = new A();
		a2.setId(3);
		a2.setAge(22);
		a2.setName("a2");
		
		A a3 = new A();
		a3.setId(4);
		a3.setAge(22);
		a3.setName("a3");
		
		List<A> list = new ArrayList<>();
		list.add(a3);
		list.add(a2);
		list.add(a1);
		list.add(a);
		
		List<Integer> list1 = list.stream().map(A::getId).collect(Collectors.toList());
		List<Integer> list2 = list.stream().map(A::getAge).collect(Collectors.toList());//未去重
		List<Integer> list3 = list.stream().map(A::getAge).distinct().collect(Collectors.toList());//已去重
		System.out.println(list1);
		System.out.println(list2);
		System.out.println(list3);
	}
	
	static class A{
		private Integer id;
		private Integer age;
		private String name;
		public Integer getId() {
			return id;
		}
		public void setId(Integer id) {
			this.id = id;
		}
		public Integer getAge() {
			return age;
		}
		public void setAge(Integer age) {
			this.age = age;
		}
		public String getName() {
			return name;
		}
		public void setName(String name) {
			this.name = name;
		}
	}

}

返回结果