/**
 * Created by yywang on 2017/1/14.
 */
class stack{
    private String [] a;
    private int N;
    stack(int cap){
        a = new String[cap];
    }
    void push(String o){
        a[N] = o;
        N++;
    }
    String pop(){
        N--;
        return a[N];
    }
    boolean isEmpty(){
        return N==0;
    }

    int size(){
        return N;
    }

}

public class FixedCapaticyStackOfString

上面实现的stack中的元素必须是String， 下面使用泛型编程，来扩大stack中可以容纳的类型。

/**
 * Created by yywang on 2017/1/14.
 */
class stack<Item>{
    private Item [] a;
    private int N;
    stack(int cap){
        a = (Item [])new Object[cap];
    }
    void push(Item o){
        a[N] = o;
        N++;
    }
    Item pop(){
        N--;
        return a[N];
    }
    boolean isEmpty(){
        return N==0;
    }

    int size(){
        return N;
    }

}

public class FixedCapaticyStack