单层for循环将两个List根据某个相同字段来进行合并

超、凢脫俗 2022-12-20 02:12 157阅读 0赞

功能实现的过程中用到了map，就是拿空间换时间的解决思路。废话不多说，直接上代码

### 1 两个基类 ###

##### 1.1 Student #####

package com.test.list;
    
    /** * @author mazhen * @className Student * @Description 学生类 * @date 2020/11/9 15:20 */
    public class Student { 
    
        private Long id;
        private String name;
        private int age;
        private Long classId;
        private String className;
    
        public Student(Long id, String name, int age, Long classId) { 
            this.id = id;
            this.name = name;
            this.age = age;
            this.classId = classId;
        }
    
        public Long getId() { 
            return id;
        }
    
        public void setId(Long id) { 
            this.id = id;
        }
    
        public String getName() { 
            return name;
        }
    
        public void setName(String name) { 
            this.name = name;
        }
    
        public int getAge() { 
            return age;
        }
    
        public void setAge(int age) { 
            this.age = age;
        }
    
        public Long getClassId() { 
            return classId;
        }
    
        public void setClassId(Long classId) { 
            this.classId = classId;
        }
    
        public String getClassName() { 
            return className;
        }
    
        public void setClassName(String className) { 
            this.className = className;
        }
    
        @Override
        public String toString() { 
            return "Student{" +
                    "id=" + id +
                    ", name='" + name + '\'' +
                    ", age=" + age +
                    ", classId=" + classId +
                    ", className='" + className + '\'' +
                    '}';
        }
    }

##### 1.2 Class #####

package com.test.list;
    
    /** * @author mazhen * @className Class * @Description 班级类 * @date 2020/11/9 15:24 */
    public class Class { 
        private Long id;
        private String name;
    
        public Class(Long id, String name) { 
            this.id = id;
            this.name = name;
        }
    
        public Long getId() { 
            return id;
        }
    
        public void setId(Long id) { 
            this.id = id;
        }
    
        public String getName() { 
            return name;
        }
    
        public void setName(String name) { 
            this.name = name;
        }
    
        @Override
        public String toString() { 
            return "Class{" +
                    "id=" + id +
                    ", name='" + name + '\'' +
                    '}';
        }
    }

### 2 功能实现 ###

package com.test.list;
    
    import java.util.ArrayList;
    import java.util.List;
    import java.util.Map;
    import java.util.function.Function;
    import java.util.stream.Collectors;
    
    /** * @author mazhen * @className ListCombine * @Description 单层for循环将两个List根据某个相同字段来进行合并 * @date 2020/11/9 15:19 */
    public class ListCombine { 
        static List<Student> studentList = new ArrayList<>();
        static List<Class> classList = new ArrayList<>();
        static { 
            studentList.add(new Student(1L,"张三",18,1L));
            studentList.add(new Student(2L,"李四",19,2L));
            studentList.add(new Student(3L,"王五",19,3L));
    
            classList.add(new Class(1L,"高三(1)班"));
            classList.add(new Class(2L,"高三(2)班"));
            classList.add(new Class(3L,"高三(3)班"));
        }
    
        public static void main(String[] args) { 
            System.out.println("合并前:"+ studentList);
            Map<Long,Class> map = classList.stream().collect(Collectors.toMap(Class::getId, Function.identity()));
            studentList.forEach(student -> { 
               if (map.containsKey(student.getClassId())) { 
                  Class class1 = map.get(student.getClassId());
                  student.setClassName(class1.getName());
               }
            });
            System.out.println("合并后:"+studentList);
        }
        
    }

### 3 结果输出 ###

![在这里插入图片描述][watermark_type_ZmFuZ3poZW5naGVpdGk_shadow_10_text_aHR0cHM6Ly9ibG9nLmNzZG4ubmV0L21hbWVuZzE5ODg_size_16_color_FFFFFF_t_70_pic_center]

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