第十一讲：享元模式

享元,享,就是分享,元,就是数据.共享数据减少内存占用.

Flyweight:轻量级.享元模式的核心就是享元工厂.享元模式在后面Java EE学到的自定义连接池的原理是一样的.

public class MainClass {
    /**
     * 
     * @param args
     */
     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){//myChar1和myChar3共享的数据相同,但是它们却不是同一个对象.
            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){//因为myChar1和myChar3是同一个对象.
             
             System.out.println(true);
         }else{
             System.out.println(false);
         }
         
    }
}

public class MyCharacter {
     private char mychar;

    public MyCharacter(char mychar) {
        super();
        this.mychar = mychar;
    }
    
    public void display(){
        System.out.println(mychar);
    }
    
     
     
}

import java.util.HashMap;
import java.util.Map;

//享元工厂
public class MyCharacterFactory {
      private Map<Character,MyCharacter>   pool   ;//Character是泛型,后面是我们自定义的MyCharacter

    public MyCharacterFactory() {
        super();
        pool = new HashMap<Character,MyCharacter>();//HashMap是一个键值对,键是一个字符,值是MyCharacter这个自定义对象
        //那么需要传这个键才能找到这个值.
        
    }
    public MyCharacter getMyCharacter(Character character){
        MyCharacter myChar = pool.get(character);
        
        if(myChar == null){//如果pool里面没有键相对应的那个值
            myChar = new MyCharacter(character);
            pool.put(character,myChar);
        }
        
        
        
        return myChar;
        
    }
    
}

---

再做一个应用。

抽象享元角色Person

具体享元角色Teacher

package com.ibeifeng.news;

public class MainClass {
    public static void main(String[] args) {
        TeacherFactory factory = new TeacherFactory();
        Teacher teacher1 = factory.getTeacher("0102034");
        Teacher teacher2 = factory.getTeacher("0102035");
        //Teacher teacher3 = factory.getTeacher("0102036");
        Teacher teacher3 = factory.getTeacher("0102034");
        
        Teacher teacher4 = factory.getTeacher("0102037");
        
        System.out.println(teacher1.getNumber());
        System.out.println(teacher2.getNumber());
        System.out.println(teacher3.getNumber());
        System.out.println(teacher4.getNumber());
        //Teacher1和Teacher3的number相同,它是同一个对象.
        if(teacher1==teacher3){
            System.out.println("true");
        }else{
            System.out.println(false);
        }
    }
}

package com.ibeifeng.news;

public class Person {
     private String name;
     private int age;
     private String sex;
    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;
    }
    public Person(String name, int age, String sex) {
        super();
        this.name = name;
        this.age = age;
        this.sex = sex;
    }
    public Person() {
        super();
        
    }
     
}

package com.ibeifeng.news;

public class Teacher extends Person{
    //private int number;//int的NO比较受限,教师号可能是0开头或者是050几
    private String number;
    
    /* public Teacher(String name, int age, String sex,int number) {
        super(name, age, sex);
        this.number = number;
    }
*/

/*    public int getNumber() {
        return number;
    }
*/

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

    public String getNumber() {
        return number;
    }

    public void setNumber(String number) {
        this.number = number;
    }

    public Teacher() {
        super();
        // TODO Auto-generated constructor stub
    }




/*    public void setNumber(int number) {
        this.number = number;
    }*/





     
}

package com.ibeifeng.news;

import java.util.HashMap;
import java.util.Map;

public class TeacherFactory {
     private Map<String,Teacher> pool;//通过Teacher的number找到这样一个老师,number是String类型的.

    public TeacherFactory() {
        super();
         pool = new HashMap<String,Teacher>();
    }
  
  public Teacher getTeacher(String number){
      Teacher teacher = pool.get(number);
      if(teacher==null){//没有teacher的话我们需要构造这样一个teacher
          teacher = new Teacher();//
          teacher.setNumber(number);
          pool.put(number, teacher);
      }
      return teacher;
  }













}