java Howto ArrayList 的入栈、出栈、移位和取消移位

使用ArrayList实现入栈、出栈、移位和取消移位是Java编程中常见的操作。ArrayList是Java提供的一个动态数组类，可以方便地进行元素的添加、删除和查询。本文将介绍如何使用ArrayList实现这些操作，并且提供相应的代码示例。

java
import java.util.ArrayList;
public class StackExample {
    private ArrayList stack;
    public StackExample() {
        stack = new ArrayList<>();
    }
    public void push(int element) {
        stack.add(element);
    }
}

java
public int pop() {
    if (stack.isEmpty()) {
        throw new IllegalStateException("Stack is empty");
    }
    return stack.remove(stack.size() - 1);
}

java
public void shift() {
    if (stack.size() < 2) {
        throw new IllegalStateException("Stack size is less than 2");
    }
    int lastElement = stack.remove(stack.size() - 1);
    stack.add(0, lastElement);
}

java
public void unshift() {
    if (stack.size() < 2) {
        throw new IllegalStateException("Stack size is less than 2");
    }
    int firstElement = stack.remove(0);
    stack.add(firstElement);
}