享元模式 Flyweight Pattern

一、什么是享元模式
Flyweight模式也叫享元模式，是构造型模式之一，它通过与其他类似对象共享数据来减小内存占用。

二、享元模式的结构
see the picture



三、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实现类，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。

MyCharacter.javapublic class MyCharacter {     private char mychar;      public MyCharacter(char mychar) {         this.mychar = mychar;     }      public void display() {         System.out.println(mychar);     } }MyCharacterFactory.javaimport java.util.HashMap; import java.util.Map;   public class MyCharacterFactory {     private Map<Character,MyCharacter> pool;      public MyCharacterFactory() {         pool = new HashMap<Character,MyCharacter>();     }      public MyCharacter getMyCharacter(Character character) {         MyCharacter myChar = pool.get(character);         if(myChar == null) {             myChar = new MyCharacter(character);             pool.put(character, myChar);         }         return myChar;     } }MainClass.javapublic class MainClass {      public static void main(String[] args) { //      MyCharacter myChar1 = new MyCharacter('a'); //      MyCharacter myChar2 = new MyCharacter('b'); //      MyCharacter myChar3 = new MyCharacter('a'); //      MyCharacter myChar4 = new MyCharacter('d'); // //      myChar1.display(); //      myChar2.display(); //      myChar3.display(); //      myChar4.display(); // //      if(myChar1 == myChar3) { //          System.out.println("true"); //      } else { //          System.out.println("false"); //      }         //1.创建MyCharacter工厂         MyCharacterFactory factory = new MyCharacterFactory();          //2.从工厂中取出相应的MyCharacter         MyCharacter myChar1 = factory.getMyCharacter('a');         MyCharacter myChar2 = factory.getMyCharacter('b');         MyCharacter myChar3 = factory.getMyCharacter('a');         MyCharacter myChar4 = factory.getMyCharacter('d');          myChar1.display();         myChar2.display();         myChar3.display();         myChar4.display();          if(myChar1 == myChar3) {             System.out.println("true");         } else {             System.out.println("false");         }     }  }