Java Stack 堆栈概念

堆栈(Stack)，是计算机科学中一种特殊的串列形式的抽象数据类型，只允许在栈顶进行 push 和 pop 操作，按照后进先出的规则。
继承 Vector 类

public
class Stack<E> extends Vector<E> {
    /**
     * Creates an empty Stack.
     */
    public Stack() {
    }
    /**
     * push 输入对象
     */
    public E push(E item) {
        addElement(item);
        return item;
    }
    /**
     * pop 输出栈顶对象
     */
    public synchronized E pop() {
        E       obj;
        int     len = size();
        obj = peek();
        removeElementAt(len - 1);
        return obj;
    }
    /**
     * 查看 栈顶 对象
     */
    public synchronized E peek() {
        int     len = size();
        if (len == 0)
            throw new EmptyStackException();
        return elementAt(len - 1);
    }
    /**
     * 判断 堆栈是否为空
     */
    public boolean empty() {
        return size() == 0;
    }
    /**
     * 返回对象在堆栈中距离栈顶的距离
     */
    public synchronized int search(Object o) {
        int i = lastIndexOf(o);
        if (i >= 0) {
            return size() - i;
        }
        return -1;
    }
    /** use serialVersionUID from JDK 1.0.2 for interoperability */
    private static final long serialVersionUID = 1224463164541339165L;
}

测试 Stack 方法

public class StackTest {
    public static void main(String[] args) {
        Stack<Integer> stack = new Stack<>();
        stack.push(0);
        stack.push(1);
        stack.push(2);
        stack.push(3);
        stack.push(4);
        System.out.println("1----->栈顶------->" + stack.peek());
        stack.pop();
        System.out.println("2----->栈顶 pop 后------->" + stack.peek());
        stack.push(5);
        System.out.println("3----->栈顶 push 5 后------->" + stack.peek());
        System.out.println("4----->判断是否为空------->" + stack.empty());
        System.out.println("5----->查询 3 在堆栈中与栈顶的距离------->" + stack.search(3));
    }
}