infix to postfix in java using stack class

I'm trying to write infix to postfix program in java using stack. Here is my code:

import java.io.*;
import java.util.*;
public class ONP{
        public static void main(String args[]) throws java.io.IOException, NumberFormatException ,EmptyStackException{
            BufferedReader br= new BufferedReader(new InputStreamReader(System.in));

            int n=Integer.parseInt(br.readLine());
            StringBuilder out= new StringBuilder();

            Stack st=new Stack();

            for(int i=0;i<n;i++){
                String input=br.readLine();
                char in[]=input.toCharArray();
                int len=input.length();
                for (int j=0;j<len;j++){
                    if (in[j]>='a' && in[j]<='z'){
                        out.append(in[j]);
                    }

                    else if(in[j]=='('){
                        st.push(new Character(in[j]));

                    }
                    else if(in[j]=='+' || in[j]=='-' || in[j]=='*' || in[j]=='/' || in[j]=='^'){
                        st.push(new Character(in[j]));

                    }

                    else if(in[j]==')'){
                        int k=j;

                        while(in[k]!='(' && !st.empty() ){

                            char ch=st.pop().toString().charAt(0);
                            if(ch!='('&&ch!=')')
                             out.append(ch);
                            k--;
                        }
                    }


                }
                out.append("\n");

            }
            System.out.print(out);
        }
}

Input:

 ((a+t)*((b+(a+c))^(c+d)))

Output:

 at+bac++*cd+^

"*" should come after "+^" but it comes after "++". I can't find the bug.