JAVA【设计模式】迪⽶特原则
一、设计模式的规范
设计模式遵循六⼤原则；单⼀职责( ⼀个类和⽅法只做⼀件事 )、⾥⽒替换( 多态，⼦类可扩展⽗类 )、依赖
倒置( 细节依赖抽象，下层依赖上层 )、接⼝隔离( 建⽴单⼀接⼝ )、迪⽶特原则( 最少知道，降低耦合 )、开闭
原则( 抽象架构，扩展实现 )，会在具体的设计模式章节中，进⾏体现。
二、迪⽶特原则
定义：对象的特有功能越少被依赖和引用最好，最少知道对象特定的功能
三、示例
模拟场景：
1、例如：产品经理交给你一个需求，按本来的逻辑是你按时实现他的需求。但是某天你碰到了一个很古怪的产品经理，非得天天盯着你的活，一直在旁边催促你的进度，甚至对你的代码指手画脚。。。最终导致了你的心态崩溃，项目继续不下去了
2：例如：学校的校长想要知道学校每个班的成绩情况，校长是不需要关注每个同学的名字和成绩，他只需要询问各个班的老师最终成绩情况，得到结果
未遵守迪⽶特原则设计
学生类:Student
package com.qf.principle.dimit.tradition;
/**
* @description: 学生
*/
public class Student {
private String name; // 学生姓名
private int rank; // 考试排名(总排名)
private double grade; // 考试分数(总分)
public Student() {
}
public Student(String name, int rank, double grade) {
this.name = name;
this.rank = rank;
this.grade = grade;
}
public String getName() {
return name;
}
public void setName(String name) {
this.name = name;
}
public int getRank() {
return rank;
}
public void setRank(int rank) {
this.rank = rank;
}
public double getGrade() {
return grade;
}
public void setGrade(double grade) {
this.grade = grade;
}
}
老师类：Teacher
package com.qf.principle.dimit.tradition;
import java.util.ArrayList;
import java.util.List;
/**
* @description: 老师
*/
public class Teacher {
private String name; // 老师名称
private String clazz; // 班级
private static List<Student> studentList; // 学生
public Teacher() {
}
public Teacher(String name, String clazz) {
this.name = name;
this.clazz = clazz;
}
static {
studentList = new ArrayList<>();
studentList.add(new Student("花花", 10, 589));
studentList.add(new Student("豆豆", 54, 356));
studentList.add(new Student("秋雅", 23, 439));
studentList.add(new Student("皮皮", 2, 665));
studentList.add(new Student("蛋蛋", 19, 502));
}
public static List<Student> getStudentList() {
return studentList;
}
public String getName() {
return name;
}
public String getClazz() {
return clazz;
}
}
校长类：Principal
package com.qf.principle.dimit.tradition;
import java.util.HashMap;
import java.util.Map;
/**
* @description: 校长
*/
public class Principal {
private Teacher teacher = new Teacher("丽华", "3年1班");
// 查询班级信息，总分数、学生人数、平均值
public Map<String, Object> queryClazzInfo(String clazzId) {
// 获取班级信息；学生总人数、总分、平均分
int stuCount = clazzStudentCount();
double totalScore = clazzTotalScore();
double averageScore = clazzAverageScore();
// 组装对象，实际业务开发会有对应的类
Map<String, Object> mapObj = new HashMap<>();
mapObj.put("班级", teacher.getClazz());
mapObj.put("老师", teacher.getName());
mapObj.put("学生人数", stuCount);
mapObj.put("班级总分数", totalScore);
mapObj.put("班级平均分", averageScore);
return mapObj;
}
// 总分
public double clazzTotalScore() {
double totalScore = 0;
for (Student stu : Teacher.getStudentList()) {
totalScore += stu.getGrade();
}
return totalScore;
}
// 平均分
public double clazzAverageScore(){
double totalScore = 0;
for (Student stu : Teacher.getStudentList()) {
totalScore += stu.getGrade();
}
return totalScore / Teacher.getStudentList().size();
}
// 班级人数
public int clazzStudentCount(){
return Teacher.getStudentList().size();
}
}
迪⽶特原则设计
学生类:Student
package com.qf.principle.dimit.tradition;
/**
* @description: 学生
*/
public class Student {
private String name; // 学生姓名
private int rank; // 考试排名(总排名)
private double grade; // 考试分数(总分)
public Student() {
}
public Student(String name, int rank, double grade) {
this.name = name;
this.rank = rank;
this.grade = grade;
}
public String getName() {
return name;
}
public void setName(String name) {
this.name = name;
}
public int getRank() {
return rank;
}
public void setRank(int rank) {
this.rank = rank;
}
public double getGrade() {
return grade;
}
public void setGrade(double grade) {
this.grade = grade;
}
}
老师类：Teacher
package com.qf.principle.dimit.tradition;
import java.util.ArrayList;
import java.util.List;
/**
* @description: 老师
*/
public class Teacher {
private String name; // 老师名称
private String clazz; // 班级
private static List<Student> studentList; // 学生
public Teacher() {
}
public Teacher(String name, String clazz) {
this.name = name;
this.clazz = clazz;
}
static {
studentList = new ArrayList<>();
studentList.add(new Student("花花", 10, 589));
studentList.add(new Student("豆豆", 54, 356));
studentList.add(new Student("秋雅", 23, 439));
studentList.add(new Student("皮皮", 2, 665));
studentList.add(new Student("蛋蛋", 19, 502));
}
public static List<Student> getStudentList() {
return studentList;
}
public String getName() {
return name;
}
public String getClazz() {
return clazz;
}
// 总分
public double clazzTotalScore() {
double totalScore = 0;
for (Student stu : Teacher.getStudentList()) {
totalScore += stu.getGrade();
}
return totalScore;
}
// 平均分
public double clazzAverageScore(){
double totalScore = 0;
for (Student stu : Teacher.getStudentList()) {
totalScore += stu.getGrade();
}
return totalScore / Teacher.getStudentList().size();
}
// 班级人数
public int clazzStudentCount(){
return Teacher.getStudentList().size();
}
}
校长类：Principal
package com.qf.principle.dimit.tradition;
import java.util.HashMap;
import java.util.Map;
/**
* @description: 校长
*/
public class Principal {
private Teacher teacher = new Teacher("丽华", "3年1班");
// 查询班级信息，总分数、学生人数、平均值
public Map<String, Object> queryClazzInfo(String clazzId) {
// 获取班级信息；学生总人数、总分、平均分
int stuCount = clazzStudentCount();
double totalScore = clazzTotalScore();
double averageScore = clazzAverageScore();
// 组装对象，实际业务开发会有对应的类
Map<String, Object> mapObj = new HashMap<>();
mapObj.put("班级", teacher.getClazz());
mapObj.put("老师", teacher.getName());
mapObj.put("学生人数", stuCount);
mapObj.put("班级总分数", totalScore);
mapObj.put("班级平均分", averageScore);
return mapObj;
}
}
测试
package com.qf.principle.dimit.desgin;
import com.alibaba.fastjson.JSON;
import java.util.Map;
public class ApiTest {
public static void main(String[] args) {
Principal principal = new Principal();
Map<String, Object> map = principal.queryClazzInfo("3年1班");
String s = JSON.toJSONString(map);
System.out.println(s);
}
}
总结：
迪⽶特原则每个类只需要实现自己的单一职责和功能，不用管的太宽泛
