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());
         }
     }
 }