Example of decorator pattern

Decorator.java

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package com.mycompany.teste;

import java.util.HashMap;
import java.util.Map;

/**
 *
 * @author danilo
 */
public class Decorator {

    public static void main(String[] args) {
        Func fib = new Timed(new Memoeized(new Fibonacci()), "fib" );        
        fib.apply(40);
        fib.apply(40);
    }

}

interface Func {
    double apply(double x);
}

class Fibonacci implements Func {

    @Override
    public double apply(double x) {
        return (double) fibonacci((int) x);
    }

    public long fibonacci(int n) {
        if (n <= 1) {
            return n;
        } else {
            return fibonacci(n - 1) + fibonacci(n - 2);
        }
    }

}

class Memoeized implements Func{
    private Map<Double, Double> cache = new HashMap<>();
    private Func func;

    public Memoeized(Func func) {
        this.func = func;
    }        

    @Override
    public double apply(double x) {
        if (cache.containsKey(x)){
            return cache.get(x);
        }
        double val = func.apply(x);
        cache.put(x, val);
        return val;
    }  
    
}

class Timed implements Func{

    private Func func;
    private String name;

    public Timed(Func func, String name) {
        this.func = func;
        this.name = name;
    }   
        
    
    @Override
    public double apply(double x) {
        long t1 = System.currentTimeMillis();
        double val = func.apply(x);
        long t2 = System.currentTimeMillis();
        double diff = (t2 - t1) / 1000.0;
        System.out.println("Time to finish " + name + ": " + diff );
        return val;        
    }
    
}