第十四讲、享元模式

1.定义

Flyweight模式也叫享元模式，是结构型模式之一。它通过与其它类似对象共享数据来减少内存使用。

2.享元模式结构

  

3.享元模式的角色和职责

• 抽象享元角色：所有具体享元类的父类，规定一些需要实现的公共接口
• 具体享元角色：抽象享元角色的具体类，并实现了抽象享元角色规定的方法
• 享元工厂角色：负责创建和管理享元角色

4.代码演示

package test.com.flyweight;
/*
 * 抽象享元角色
 */
public class Person {
    private String name;
    private int age;
    private String sex;
    
    public Person(String name, int age, String sex) {
        super();
        this.name = name;
        this.age = age;
        this.sex = sex;
    }
    
    public Person() {
        
    }
    
    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 String getSex() {
        return sex;
    }

    public void setSex(String sex) {
        this.sex = sex;
    }
    
}

package test.com.flyweight;
/*
 * 具体享元角色
 */
public class Teacher extends Person {
    private String num;

    public Teacher(String name, int age, String sex, String num) {
        super(name, age, sex);
        this.num = num;
    }
    
    public Teacher() {
        super();
    }

    public String getNum() {
        return num;
    }

    public void setNum(String num) {
        this.num = num;
    }
    
}

package test.com.flyweight;

import java.util.HashMap;
import java.util.Map;
/*
 * 享元工厂角色
 */
public class FlyWeightFactory {
    private Map<String, Teacher> pool;
    
    public FlyWeightFactory() {
        pool = new HashMap<String, Teacher>();
    }
    
    public Teacher getTeacher(String num) {
        Teacher teacher = pool.get(num);
        if(teacher == null) {
            teacher = new Teacher();
            teacher.setNum(num);
            pool.put(num, teacher);
        }
        return teacher;
    }
}

package test.com.flyweight;
/*
 * 测试代码
 */
public class Main {
    public static void main(String[] args) {
        FlyWeightFactory fwf = new FlyWeightFactory();
        Teacher teacher1 = fwf.getTeacher("01");
        Teacher teacher2 = fwf.getTeacher("02");
        Teacher teacher3 = fwf.getTeacher("03");
        Teacher teacher4 = fwf.getTeacher("02");
        
        System.out.println(teacher1.getNum());
        System.out.println(teacher2.getNum());
        System.out.println(teacher3.getNum());
        System.out.println(teacher4.getNum());
        
        if(teacher2 == teacher4) {
            System.out.println("true");
        } else {
            System.out.println("false");
        }
    }
}