栈的压入、弹出序列

import java.util.ArrayList;
import java.util.Stack;
public class Solution {
    public boolean IsPopOrder(ArrayList<Integer> pushA,ArrayList<Integer> popA) {
        Stack stack = new Stack();
        if( pushA.size() == 0 && popA.size() == 0 ) return true;
        for( int i=0,j=0; i < pushA.size(); i++ ){
            stack.push( pushA.get(i) );
            while( ( !stack.empty() )&& ( stack.peek() == popA.get(j) ) ){
                stack.pop();
                j ++;
            } 
        }
         
        return stack.empty() == true;
    }
}