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。

实现步骤

• 创建一个实体类,

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

• 创建一个工厂，生成基于给定信息的实体类的对象。

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;
	}
}

• 之前我们创建对象是直接new一个，如：

MyCharacter myChar1 = new MyCharacter('a');
MyCharacter myChar2 = new MyCharacter('b');
MyCharacter myChar3 = new MyCharacter('a');
MyCharacter myChar4 = new MyCharacter('d');

• 但是我们发现1和3的数据一样，所以我们可以用享元模式模式，从工厂中获取对象，工厂会根据对象数据判断是否有相同数据的对象，如果有直接返回，没有再创建

public class MainClass {
    
    

	public static void main(String[] args) {
    
    	
		MyCharacterFactory factory = new MyCharacterFactory();
		
		
		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");
		}
	}

}