Java实现栈

• • 栈的定义
  • 栈的操作
  • Java实现栈

栈的定义

　栈(stack)是限定在表尾进行插入和删除操作的线性表．
　栈顶和栈底：允许插入和删除的一端为栈顶(Top)，相对另一端为栈底(Buttom).
　空栈：不含任何数据的栈称为空栈．
　栈又称为先进后出（LIFO）的线性表

栈的操作

入栈：插入元素；
出栈：获取元素并移除

Java实现栈

定义节点

节点包括数据和指向下一个节点的引用

class Node{ 
    public　Integer data;
    public　Node next;   
    public Node(Integer data) {
        super();
        this.data = data;
    }
}

定义栈

分别为指向栈顶元素的引用和栈的长度．

class Stack{
    private Node top;
    private Integer size = 0;
｝

获取栈顶元素

public Integer  getTop(){       
    return top.data;
}

pop元素

获取并删除栈顶元素

public Integer pop() {      
    if(top == null) {
        return null;
    }
    else {
        Node n = top;
        top = n.next;
        Integer data = n.data;
        n  = null;
        return data;            
    }
}

push元素

public void push(Integer data) {
    Node n = new  Node(data);
    if(top == null) {
        top = n;
    }
    else {
        n.next = top;
        top  = n;
    }   
    size++;
}

清空栈

public void  clean() {
    while(top != null ) {
        Node n = top;
        top = n.next;
        n = null;
    }
    size = 0;
}

转化为String

public String toString() {
    String str = "The stack data is :";
    Node n = top; 
    while(n !=  null) {
        str += n.data + "  ";
        n = n.next;
    }
    return str;
}

测试

public static void main(String[] args) {
        // TODO Auto-generated method stub
    Stack stack = new Stack();

    stack.push(5);
    stack.push(10);
    stack.push(15);
    stack.push(25);

    System.out.println(stack.toString());       
    System.out.println("Top data :" + stack.getTop());
    System.out.println("The size is :" + stack.getSize());

    System.out.println("pop a data");
    stack.pop();
    System.out.println(stack.toString());

    System.out.println("clean the stack");      
    stack.clean();
    System.out.println(stack.toString());

}

输出

The stack data is :25  15  10  5  
Top data :25
The size is :4
pop a data
The stack data is :15  10  5  
clean the stack
The stack data is :