数据结构<十>: 线程结构 栈的两种实现

提供一个接口 

package com.mo.stack;

/**
 *  这是栈的接口，抽象数据类型
 */
public interface Stack {
  /**
   *  入栈 
   */
  void push(Object obj) throws Exception;
  /**
   * 出栈 
   */
  Object pop() throws Exception;
  /**
   *  取出栈的元素 
   */
  Object getTop() throws Exception;
  /**
   *  栈是不是为空 
   */
  boolean isEmpty();
}

用数组实现的栈

package com.mo.stack;

public class SeqStack implements Stack {
  
  private final static int defaultSize = 10;//默认创建的数组大小
  private int top;//栈顶的元素的下标
  private Object[] stack;//栈数组
  private int maxStackSize;//数组的容量
  
  public SeqStack() {
    init(defaultSize);
  }
  public SeqStack(int size) {
    init(size);
  }
  private void init(int size) {
    stack = new Object[size];
    top = 0;
    maxStackSize = size;
  }
  public void push(Object obj) throws Exception {
    if(top == maxStackSize) throw new Exception();
    stack[top] = obj;
    top++;
  }
  public Object pop() throws Exception {
    if(top == 0) throw new Exception();
    Object obj = stack[top - 1];
    top--;
    return obj;
  }
  public Object getTop() throws Exception {
    if(top < 0) throw new Exception();
    return stack[top - 1];
  }
  public boolean isEmpty() {
    return top == 0;
  }
  public static void main(String[] args) throws Exception {
    SeqStack seqStack = new SeqStack();
    for(int i = 0; i < 10; i++) {
      seqStack.push(i);
    }
    while(!seqStack.isEmpty()) {
      System.out.print(seqStack.pop());
    }
  }
}

用链表实现的栈

package com.mo.stack;

import com.mo.linList.Node;

//链表实现的堆栈
public class LinStack implements Stack{

  private Node head;//栈顶
  private int size;//栈中的元素个数
  
  public LinStack() {
    head = null;
    size = 0;
  }
  
  public void push(Object obj) throws Exception {
    Node node = new Node(obj,head);//把首节点放在新增的obj后面
    head = node;//设为当前节点
    size++;
  }

  public Object pop() throws Exception {
    if(size == 0) throw new Exception();
    Object oldHead = head.getData();//获取首节点的元素数据
    head = (Node)head.getNext();//把链表的下一个Node设为当前节点
    size--;
    return oldHead;
  }

  public Object getTop() throws Exception {
    if(size == 0) throw new Exception();
    return head.getData();
  }

  public boolean isEmpty() {
    return size == 0;
  }
  
  public static void main(String[] args) throws Exception {
    LinStack linStack = new LinStack();
    for(int i = 0; i < 10; i++) {
      linStack.push(i+1);
    }
    while(!linStack.isEmpty()) {
      System.out.print(linStack.pop());
    }
  }
  

}