lambda -- 获取集合中某个属性的所有值

爱被打了一巴掌 2023-02-26 05:24 5阅读 0赞

### 代码块 ###

**GetElementFromList.java**

package com.example.demo.util;
    
    import com.example.demo.entity.UserPO;
    
    import java.util.ArrayList;
    import java.util.List;
    import java.util.stream.Collectors;
    
    public class GetElementFromList { 
        public static void main(String[] args) { 
            //1. 初始化数据
            UserPO user1 = new UserPO(1, "java");
            UserPO user2 = new UserPO(2, "C");
            UserPO user3 = new UserPO(3, "PHP");
            List<UserPO> users = new ArrayList<>();
            users.add(user1);
            users.add(user2);
            users.add(user3);
    
            //2. 获取list集合中的某个元素
            List<Integer> ids = users.stream().map(user -> user.getId()).collect(Collectors.toList());
    
            //3. 遍历
            ids.forEach(System.out::println);
        }
    }

**UserPO.java**

package com.example.demo.entity;
    
    public class UserPO { 
        private Integer id;
        private String name;
    
        public UserPO(Integer id, String name) { 
            this.id = id;
            this.name = name;
        }
    
        public Integer getId() { 
            return id;
        }
    
        public void setId(Integer id) { 
            this.id = id;
        }
    
        public String getName() { 
            return name;
        }
    
        public void setName(String name) { 
            this.name = name;
        }
    
        @Override
        public String toString() { 
            return "User{" +
                    "id=" + id +
                    ", name='" + name + '\'' +
                    '}';
        }
    }

**输出**

1
    2
    3