Java手写实现栈【数据结构与算法】

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());
    // }
    }
    }