問題

對於內容相同的字串如“student”能夠為多個使用者所共享，而這些字串的顏色和字型可以不同。設計一個方案能支援字串的共享，同時還支援批量設定顏色或字型。

解決方案

享元模式

分析：字串可以放在池子裡，保證字串唯一，與顏色、字型類分別關聯，讓使用者設定顏色、字型。

UML類圖

原始碼

package task1;

import java.util.ArrayList;

public class WordFactory {
	//字串集合，所有字串都放在這個集合裡面
	private ArrayList<String> list = new ArrayList<String>();
	private ArrayList<Word> wordList = new ArrayList<Word>();
	
	public Word getWord(String str) {
		if(list.contains(str) == false) {
			list.add(str);
		}
		Word word = new Word(str);
		wordList.add(word);
		return word;
	}
	
	//批量設定顏色
	public void setColor(Color color) {
		for(Word word : wordList) {
			word.setColor(color);
		}
	}
	//批量設定字型
	public void setFont(Font font) {
		for(Word word : wordList) {
			word.setFont(font);
		}
	}
}

 

package task1;

public class Word {
	private String str;
	private String font = "Arial";//預設字型
	private String color = "Black";//預設顏色
	
	public Word(String str) {
		this.str = str;
	}
	public void setColor(Color color) {
		this.color = color.getColor();
	}
	public void setFont(Font font) {
		this.font = font.getFont();
	}
	@Override
	public String toString() {
		return "Word [str=" + str + ", font=" + font + ", color=" + color + "]";
	}
	
}

 

package task1;

public class Color {
	private String color;
	
	public Color(String color) {
		this.color = color;
	}
	public String getColor() {
		return this.color;
	}
}

package task1;

public class Font {
	private String font;
	
	public Font(String font) {
		this.font = font;
	}
	public String getFont() {
		return this.font;
	}
}

 

測試及結果

package task1;


public class Client {
	
	public static void main(String[] args) {
		WordFactory factory = new WordFactory();
		Word w1,w2,w3;
		w1 = factory.getWord("hello");
		w2 = factory.getWord("hello");
		w3 = factory.getWord("hello");
		
		System.out.println(w1);
		System.out.println(w2);
		System.out.println(w3);
		System.out.println("---------------------------------------------------");
		
		factory.setColor(new Color("purple"));
		factory.setFont(new Font("Tahoma"));
		System.out.println(w1);
		System.out.println(w2);
		System.out.println(w3);
		System.out.println("---------------------------------------------------");
		
		w1.setColor(new Color("red"));
		w1.setFont(new Font("font1"));
		
		w2.setColor(new Color("green"));
		w2.setFont(new Font("font2"));
		
		w3.setColor(new Color("blue"));
		w3.setFont(new Font("font3"));
		
		System.out.println(w1);
		System.out.println(w2);
		System.out.println(w3);
		
		
	}
}