Java Improvement (Sanyi)-----Stack

In Java, the Stack class represents a last-in-first-out (LIFO) object stack. The stack is a very common data structure that uses a typical first-in-last-out operation. Each stack contains a stack top. Each time the stack is popped, the data on the top of the stack is taken out, as follows:

Stack extends Vector with five operations, allowing vectors to be treated as stacks. The five operations are as follows:

##pushPush the item onto the top of the stack. searchReturns the position of the object on the stack, with 1 as the base. The implementation of

#                                                 ##                                                              Description	empty()
# Test whether the stack is empty. <strong></strong>	##peek()
View the object at the top of the stack without removing it from the stack. <strong></strong>	##pop ()
Remove the object at the top of the stack and return it as the value of this function. <strong></strong>	(E item)
<strong></strong>	(Object o)
<strong></strong>##               Stack inherits Vector, and he simply extends Vector:	public class Stack<E> extends Vector<E>

Stack is very simple, with only one construction method and five implementation methods (methods inherited from Vector are not included) ), and the source code for its implementation is very simple

/**
     * 构造函数
     */
    public Stack() {
    }

    /**
     *  push函数：将元素存入栈顶
     */
    public E push(E item) {
        // 将元素存入栈顶。
        // addElement()的实现在Vector.java中
        addElement(item);

        return item;
    }

    /**
     * pop函数：返回栈顶元素，并将其从栈中删除
     */
    public synchronized E pop() {
        E    obj;
        int    len = size();

        obj = peek();
        // 删除栈顶元素，removeElementAt()的实现在Vector.java中
        removeElementAt(len - 1);

        return obj;
    }

    /**
     * peek函数：返回栈顶元素，不执行删除操作
     */
    public synchronized E peek() {
        int    len = size();

        if (len == 0)
            throw new EmptyStackException();
        // 返回栈顶元素，elementAt()具体实现在Vector.java中
        return elementAt(len - 1);
    }

    /**
     * 栈是否为空
     */
    public boolean empty() {
        return size() == 0;
    }

    /**
     *  查找“元素o”在栈中的位置：由栈底向栈顶方向数
     */
    public synchronized int search(Object o) {
        // 获取元素索引，elementAt()具体实现在Vector.java中
        int i = lastIndexOf(o);

        if (i >= 0) {
            return size() - i;
        }
        return -1;
    }

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