Stack.java

package stack;

import java.util.ArrayList;

/**
 * Created by bdl19 on 2017/4/8.
 */
public class Stack {
    private int count;
    private ArrayList elementData;

    public Stack() {
        this.count = 0;
        elementData = new ArrayList();
    }

    public void push(Object o) {
        count++;
        elementData.add(o);

    }

    public Object pop() {
        count--;
        Object o = elementData.get(count);
        elementData.remove(count);
        return o;
    }

    public Object peek() {

        return elementData.get(count-1);
    }

    public boolean isEmpty() {
        if (count == 0) {
            return true;
        } else {
            return false;
        }
    }

    public int size() {
        return count;
    }

    public String toString(){
        StringBuilder sb = new StringBuilder();
        Stack s = new Stack();
        while(!this.isEmpty()){
            sb.append(this.peek().toString());
            sb.append(",");
            s.push(this.pop());
        }
        while(!s.isEmpty()){
            this.push(s.pop());
        }

//       sb.deleteCharAt(sb.length()-1);
        return sb.toString();
    }
}