Stack实现

栈的三种操作算法很简单

STACK-EMPTY(S)

1 if S.top == 0

2    return TRUE

3 else return FALSE

PUSH(S, x)

1 S.top = S.top + 1

2 S[S.top] = x

POP(S)

1 if STACK-EMPTY(S)

2 　　error "underflow"

3 else S.top = S.top - 1

4　　return S[S.top + 1]

Stack Java实现

package hello;

import java.util.Arrays;

public class TStack<E> {
    private int capacity = 10;
    private int capacityIncrement = 10;
    private int elementCount = 0;
    private Object[] elementData;

    public TStack(){
        this.elementData = new Object[capacity];
    }

    public boolean empty(){
        return size() == 0;
    }

    public E push(E item){
        ensureCapacity(elementCount + 1);
        this.elementData[elementCount++] = item;
        return item;
    }

    public E pop(){
        E top = (E)this.elementData[elementCount-1];
        removeElement(elementCount-1);
        return top;
    }

    public int size(){
        return elementCount;
    }

    private void ensureCapacity(int minCapacity){
        if(minCapacity - this.elementData.length > 0){
            grow();
        }
    }

    private void grow(){
        int newCapacity = this.elementData.length + this.capacityIncrement;
        this.elementData = Arrays.copyOf(this.elementData, newCapacity);
    }

    private void removeElement(int index){
        if (index >= this.elementCount){
            throw new ArrayIndexOutOfBoundsException();
        }
        elementCount--;
        this.elementData[elementCount] = null;
    }

    public static void main(String[] args){
        TStack<Integer> s = new TStack<>();
        for (int i = 0; i < 100; i++){
            s.push(i);
        }
        int n = s.size();
        for (int i = 0; i < n; i++) {
            System.out.println(s.pop());
        }
    }
}