프록시 패턴과 객체

// interface Calculator
public interface Calculator {
	public long factorial(long num);
}

// class ImpeCalculator
public class ImpeCalculator implements Calculator {

	@Override
	public long factorial(long num) {
		long result = 1;
		for (long i = 1; i <= num; ++i) result *= i;
		return result;
	}
}

// class ProxyCalculator
public class ProxyCalculator implements Calculator {

	private Calculator delegate;
	
	public ProxyCalculator(Calculator delegate) {
		this.delegate = delegate;
	}
	
	@Override
	public long factorial(long num) {
		
		long start = System.nanoTime();
		long result = delegate.factorial(num);
		long end = System.nanoTime();
		
		System.out.printf("%s.factorial(%d) 실행시간 = %d\n", delegate.getClass().getSimpleName(), num, (end - start));
		return result;
	}
}

// class Main
public class Main {

	public static void main(String[] args) {
		
		Calculator cal = new ImpeCalculator();
		Calculator proxyCal = new ProxyCalculator(cal);
		
		System.out.println(cal.factorial(5));
		System.out.println(proxyCal.factorial(5));		
	}
}

120
ImpeCalculator.factorial(5) 실행시간 = 1600
120