栈Stack的实现【java】

In computer science, a stack is a last in, first out (LIFO) abstract data type and linear data structure. A stack can have any abstract data type as an element, but is characterized by only three fundamental operations: push, popand stack top. The push operation adds a new item to the top of the stack, or initializes the stack if it is empty. If the stack is full and does not contain enough space to accept the given item, the stack is then considered to be in an overflow state. The pop operation removes an item from the top of the stack. A pop either reveals previously concealed items, or results in an empty stack, but if the stack is empty then it goes into underflow state (It means no items are present in stack to be removed). The stack top operation gets the data from the top-most position and returns it to the user without deleting it. The same underflow state can also occur in stack top operation if stack is empty.

A stack is a restricted data structure, because only a small number of operations are performed on it. The nature of the pop and push operations also means that stack elements have a natural order. Elements are removed from the stack in the reverse order to the order of their addition: therefore, the lower elements are those that have been on the stack the longest.

                                           ---from wikipedia(http://en.wikipedia.org/wiki/Stack_(data_structure))

栈的java实现：

package com.matrix.stack;

import java.util.ArrayList;
import java.util.List;

public class Stack {

    // 栈的数据区
    private List<Object> list;
    // 栈顶指针
    private int topPointer;

    public Stack() {
        this.list = new ArrayList();
        this.topPointer = -1;
    }

    public Stack(List<Object> list, int topPointer) {
        if (null == list) {
            list = new ArrayList();
        }
        this.list = list;
        this.topPointer = list.size() - 1;
    }

    /**
     * 入栈方法
     * 
     * @Description: TODO
     * @param @param Object
     * @return void
     * @throws
     * @author Matrix
*/
    public void push(Object Object) {
        this.list.add(Object);
        topPointer++;
    }

    /**
     * 出栈方法
     * 
     * @Description: TODO
     * @param @return
     * @return Object
     * @throws
     * @author Matrix
*/
    public Object pop() {
        if (!isEmpty()) {
            Object obj = this.list.remove(this.topPointer);
            this.topPointer--;
            return obj;
        } else {
            return null;
        }
    }

    /**
     * 判断栈是否为空
     * 
     * @Description: TODO
     * @param @return
     * @return boolean
     * @throws
     * @author Matrix
*/
    public boolean isEmpty() {
        if (topPointer == -1) {
            return true;
        } else {
            return false;
        }
    }

    /**
     * 获取栈的大小
     * 
     * @Description: TODO
     * @param @return
     * @return int
     * @throws
     * @author Matrix
*/
    public int getStackSize() {
        return this.list.size();
    }

    /**
     * 返回栈顶元素
     * 
     * @Description: TODO
     * @param @return
     * @return Object
     * @throws
     * @author Matrix
*/
    public Object top() {
        if (topPointer == -1) {
            return null;
        } else {
            return list.get(topPointer);
        }
    }

    /**
     * 打印栈的内部数据信息
     * 
     * @Description: TODO
     * @param
     * @return void
     * @throws
     * @author Matrix
*/
    public void printStack() {
        if (this.list.size() > 0) {
            System.out.println("The data int stack is:");
            for (int i = 0; i < list.size(); i++) {
                System.out.print(this.list.get(i).toString() + "  ");
            }
            System.out.println();
        } else {
            System.out.println("The stack is empty!");
        }
    }

    public List<Object> getList() {
        return list;
    }

    public void setList(List<Object> list) {
        this.list = list;
    }

    public int getTopPointer() {
        return topPointer;
    }

    public void setTopPointer(int topPointer) {
        this.topPointer = topPointer;
    }
}

测试类

package com.matrix.stack;

import org.junit.Test;

public class StackTest {

    @Test
    public void stackTest(){
        Stack stack= new Stack();
        int i=5;
        stack.push(i);
        String str="Matrix";
        stack.push(str);
        double d=1.2345;
        stack.push(d);
        System.out.println(stack.top());
        stack.printStack();
        stack.pop();
        stack.printStack();
        stack.pop();
        stack.printStack();
        stack.pop();
        stack.printStack();
    }
}

 

 

一步一步往上爬......