leetcode--002 rpn

 package leetcode;

 import java.util.Stack;

 public class RPN {
      public static int evalRPN(String[] tokens) {
          Stack stack=new Stack();
             for(int i=0;i<tokens.length;i++){
                 if(tokens[i]=="+"){
                     int a=Integer.parseInt((String)stack.pop());
                     int b=Integer.parseInt((String)stack.pop());
                     stack.push(a+b);
                 }else if(tokens[i]=="-"){
                     int a=Integer.parseInt((String)stack.pop());
                     int b=Integer.parseInt((String)stack.pop());
                     stack.push(a-b);
                 }else if(tokens[i]=="*"){
                     int a=Integer.parseInt((String)stack.pop());
                     int b=Integer.parseInt((String)stack.pop());
                     stack.push(a*b);
                 }else if(tokens[i]=="/"){
                     int a=Integer.parseInt((String)stack.pop());
                     int b=Integer.parseInt((String)stack.pop());
                     if(b==0){
                         return 0;

                     }else{
                         stack.push(a/b);
                     }

                 }else{
                     stack.push(tokens[i]);
                 }

             }
             int result=(int)stack.peek();
             return result;
         }
      public static void main(String[] args){
          String[] tokens={"0","3","/"};

          System.out.println(evalRPN(tokens));
      }
 }