This gist belongs to Clean Code Cookbook http://cleancodecookbook.com By Maximiliano Contieri http://maximilianocontieri.com

subclassification.java

class Stack extends ArrayList {
    public void push(Object value) { … }
    public Object pop() { … }
}

// Stack doesn't behave Like an ArrayList
// besides pop, push, top it also implements (or overrides) 
// get, set, add, remove and clear
// stack elements can be arbitrary accessed

// both classes are concrete