Приспособленец (шаблон проектирования) 📖 Wikipedia

import java.util.*;

public enum FontEffect {
    BOLD, ITALIC, SUPERSCRIPT, SUBSCRIPT, STRIKETHROUGH
}

public final class FontData {
    /**
     * A weak hash map will drop unused references to FontData.
     * Values have to be wrapped in WeakReferences, 
     * because value objects in weak hash map are held by strong references.
     */
    private static final WeakHashMap<FontData, WeakReference<FontData>> flyweightData =
        new WeakHashMap<FontData, WeakReference<FontData>>();
    private final int pointSize;
    private final String fontFace;
    private final Color color;
    private final Set<FontEffect> effects;

    private FontData(int pointSize, String fontFace, Color color, EnumSet<FontEffect> effects) {
        this.pointSize = pointSize;
        this.fontFace = fontFace;
        this.color = color;
        this.effects = Collections.unmodifiableSet(effects);
    }

    public static FontData create(int pointSize, String fontFace, Color color,
        FontEffect... effects) {
        EnumSet<FontEffect> effectsSet = EnumSet.noneOf(FontEffect.class);
        effectsSet.addAll(Arrays.asList(effects));
        // We are unconcerned with object creation cost, we are reducing overall memory consumption
        FontData data = new FontData(pointSize, fontFace, color, effectsSet);
        if (!flyweightData.containsKey(data)) {
            flyweightData.put(data, new WeakReference<FontData> (data));
        }
        // return the single immutable copy with the given values
        return flyweightData.get(data).get();
    }

    @Override
    public boolean equals(Object obj) {
        if (obj instanceof FontData) {
            if (obj == this) {
                return true;
            }
            FontData other = (FontData) obj;
            return other.pointSize == pointSize && other.fontFace.equals(fontFace)
                && other.color.equals(color) && other.effects.equals(effects);
        }
        return false;
    }

    @Override
    public int hashCode() {
        return (pointSize * 37 + effects.hashCode() * 13) * fontFace.hashCode();
    }

    // Getters for the font data, but no setters. FontData is immutable.
}

public abstract class EnglishCharacter {

	protected char symbol;
	
	protected int width;
	
	protected int height;
	
	public abstract void printCharacter();
	
}

public class CharacterA extends EnglishCharacter {

	public CharacterA(){
		symbol = 'A';
		width = 10;
		height = 20;
	}
	
	@Override
	public void printCharacter() {
		System.out.println("Symbol = " + symbol + " Width = " + width + " Height = " + height);
	}
	
}

public class CharacterB extends EnglishCharacter {

	public CharacterB(){
		symbol = 'B';
		width = 20;
		height = 30;
	}
	
	@Override
	public void printCharacter() {
		System.out.println("Symbol = " + symbol + " Width = " + width + " Height = " + height);
	}
	
}

public class CharacterC extends EnglishCharacter {

	public CharacterC(){
		symbol = 'C';
		width = 40;
		height = 50;
	}
	
	@Override
	public void printCharacter() {
		System.out.println("Symbol = " + symbol + " Width = " + width + " Height = " + height);
	}
	
}

public class FlyweightFactory {

	private HashMap<Integer, EnglishCharacter> characters = new HashMap();
	
	public EnglishCharacter getCharacter(int characterCode){
		EnglishCharacter character = characters.get(characterCode);
		if (character == null){
			switch (characterCode){
				case 1 : {
					character = new CharacterA();
					break;
				}
				case 2 : {
					character = new CharacterB();
					break;
				}
				case 3 : {
					character = new CharacterC();
					break;
				}
			}
			characters.put(characterCode, character);
		}
		return character;
	} 
	
}

/* 
 * Класс, показывающий работу шаблона проектирования "Приспособленец".
 * */

public class Application {

	public static void main (String [] args){
		FlyweightFactory factory = new FlyweightFactory();
		
		int [] characterCodes = {1,2,3};
		for (int nextCode : characterCodes){
			EnglishCharacter character = factory.getCharacter(nextCode);
			character.printCharacter();
		}
	}
	
}