Java设计模式-----FlyWeight享元模式_享元模式java设计实例-优快云博客

本文介绍了享元模式的基本概念及其在程序设计中的应用。通过具体示例展示了如何利用享元模式来减少内存消耗并提高程序效率。享元模式适用于需要创建大量相似对象的场景，能够通过共享对象减轻系统负担。

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源自：http://www.blogjava.net/flustar/archive/2008/01/26/flyw.html

FlyWeight享元模式：

运用共享技术有效地支持大量细粒度对象。

也就是说在一个系统中如果有多个相同的对象，那么只共享一份就可以了，不必每个都去实例化一个对象。在Flyweight模式中，由于要产生各种各样的对象，所以在Flyweight(享元)模式中常出现Factory模式。Flyweight的内部状态是用来共享的,Flyweight factory负责维护一个对象存储池（Flyweight Pool）来存放内部状态的对象。Flyweight模式是一个提高程序效率和性能的模式,会大大加快程序的运行速度。

例子：

public abstract class Character {

	protected char symbol;
	protected int width;
	protected int height;
	protected int ascent;
	protected int descent;
	protected int pointSize;

	public abstract void Display(int pointSize);
}

public class CharacterA extends Character {

	public CharacterA() {
		this.symbol = 'A';
		this.height = 100;
		this.width = 120;
		this.ascent = 70;
		this.descent = 0;
	}

	public void Display(int pointSize) {
		this.pointSize = pointSize;
		System.out.println(this.symbol + " (pointsize " + this.pointSize + ")");
	}
}

public class CharacterB extends Character {

	public CharacterB() {
		this.symbol = 'B';
		this.height = 100;
		this.width = 140;
		this.ascent = 72;
		this.descent = 0;
	}

	public void Display(int pointSize) {
		this.pointSize = pointSize;
		System.out.println(this.symbol + " (pointsize " + this.pointSize + ")");
	}
}

//C, D, E, etc.

public class CharacterZ extends Character {

	public CharacterZ() {
		this.symbol = 'Z';
		this.height = 100;
		this.width = 100;
		this.ascent = 68;
		this.descent = 0;
	}

	public void Display(int pointSize) {
		this.pointSize = pointSize;
		System.out.println(this.symbol + " (pointsize " + this.pointSize + ")");
	}
}

public class CharacterFactory {

	private Hashtable characters = new Hashtable();

	public Character GetCharacter(char key) {
		// Uses "lazy initialization"
		Character character = (Character) characters.get(key);
		if (character == null) {
			switch (key) {
			case 'A':
				character = new CharacterA();
				break;
			case 'B':
				character = new CharacterB();
				break;
			//
			case 'Z':
				character = new CharacterZ();
				break;
			}
			characters.put(key, character);
		}
		return character;
	}
}

public class Client {

	public static void main(String[] args) {
		
		String document = "AAZZBBZB";
		char[] chars = document.toCharArray();
		CharacterFactory f = new CharacterFactory();
		int pointSize = 10;
		for (char c : chars) {
			pointSize++;
			Character character = f.GetCharacter(c);
			character.Display(pointSize);
		}
	}
}