Java实现栈

package algorithm;

import java.util.Arrays;

import java.util.Iterator;

/**

• @author Administrator

• @date 2022-09-12 16:38

• 数组栈
  
  */
  
  public class MyArrayStack implements Iterable {
  
  // 定义一个数组
  
  private Object[] elementData;
  
  // 顶部的索引
  
  private int topIndex;
  
  // 构造方法确定栈的长度
  
  public MyArrayStack(int size) {
  
  this.elementData = new Object[size];
  
  }

  /**

  • 定义迭代器
  • @return
    
    */
    
    @Override
    
    public Iterator iterator() {
    
    return new MyArrayStackIter();
    
    }
    
    class MyArrayStackIter implements Iterator{
    
    @Override
    
    public boolean hasNext() {
    
    return topIndex != elementData.length;
    
    }
    
    @Override
    
    public E next() {
    
    return pop();
    
    }
    
    @Override
    
    public void remove() {
    
    pop();
    
    }
    
    }
    
    public boolean push(E element){
    
    // 判断扩容两倍
    
    if(topIndex >= elementData.length){
    
    elementData = Arrays.copyOf(elementData,elementData.length << 1);
    
    }
    
    elementData[topIndex++] = element;
    
    return true;
    
    }
    
    // 删除并出栈 是否删除就看topIndex本身的大小是否改变
    
    public E pop(){
    
    if(topIndex <= 0){
    
    throw new RuntimeException("栈为空");
    
    }
    
    return (E) elementData[--topIndex];
    
    }
    
    // 不删除出栈 栈顶元素
    
    public E peek(){
    
    if(topIndex <= 0){
    
    throw new RuntimeException("栈为空");
    
    }
    
    return (E) elementData[topIndex - 1];
    
    }
    
    public static void main(String[] args) {
    
    MyArrayStack myArrayStack = new MyArrayStack(5);
    
    myArrayStack.push("11");
    
    myArrayStack.push("22");
    
    myArrayStack.push("33");
    
    System.out.println("-----------");
    
    System.out.println(myArrayStack.pop());
    
    System.out.println(myArrayStack.pop());
    
    System.out.println(myArrayStack.pop());
    
    System.out.println(myArrayStack.pop());
    
    // Iterator iterator = myArrayStack.iterator();
    
    // while (iterator.hasNext()){
    
    // System.out.println(iterator.next());
    
    // }
    
    }
    
    }