Java Design Patterns परिचय

public class Main {
	static class Config implements Cloneable {
		String name;
		Config(String name) { this.name = name; }
		public Config clone() {
			try { return (Config) super.clone(); } catch (CloneNotSupportedException e) { return null; }
		}
	}
	public static void main(String[] args) {
		Config original = new Config("base");
		Config copy = original.clone(); // creates a new object by cloning, not a fresh constructor call
		System.out.println(copy.name);
	}
}

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public class Main {
	interface UsSocket { void plugUs(); }
	static class EuPlug {
		void plugEu() { System.out.println("EU plug connected"); }
	}
	static class Adapter implements UsSocket {
		EuPlug euPlug = new EuPlug();
		public void plugUs() { euPlug.plugEu(); } // translates one interface to another
	}
	public static void main(String[] args) {
		UsSocket socket = new Adapter();
		socket.plugUs();
	}
}

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public class Main {
	interface PaymentStrategy { void pay(int amount); }
	static class CardPayment implements PaymentStrategy {
		public void pay(int amount) { System.out.println("Paid " + amount + " by card"); }
	}
	static class CashPayment implements PaymentStrategy {
		public void pay(int amount) { System.out.println("Paid " + amount + " in cash"); }
	}
	public static void main(String[] args) {
		PaymentStrategy strategy = new CardPayment();
		strategy.pay(100); // swappable at runtime
	}
}

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public class Main {
	interface Factory { Object create(); } // naming this "Factory" instantly communicates the design
	public static void main(String[] args) {
		Factory factory = () -> "Shared vocabulary saves re-inventing solutions";
		System.out.println(factory.create());
	}
}

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public class Main {
	enum PatternCategory { CREATIONAL, STRUCTURAL, BEHAVIORAL }
	public static void main(String[] args) {
		PatternCategory category = PatternCategory.CREATIONAL; // identify the category first
		System.out.println("Problem falls into: " + category);
	}
}

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