javaPosfixConversion

package www;
import java.util.Scanner;
import java.util.Stack;

//////////////////////////////////////////////////////////////////

class Postfix {

   int n;
   Stack <Character> st = new Stack();

   Postfix(int total){

     n= total;
     st.push('(');

   } /// Constructor

   boolean isOperator(char c){

         if(c== '+'|| c== '-' || c=='/'||
            c=='*' || c == '%'|| c== '^') return true;

         else return false;
   } /// is operator

   boolean isOperand(char c){

       if((c>='A' && c<='Z' ) || (c>='a' && c<='z')
          || (c>='0' && c<='9') || (c==' ')|| (c=='.'))

               return true;
       else
               return false;

   } /// is operand


   int precedence(char c){

      switch(c){

          case'^' : return 3;
          case'%' : return 2;
          case'*' : return 2;
          case'/' : return 2;
          case'+' : return 1;
          case'-' : return 1;
          default : return 0;

      } /// switch

   }  /// precedence


   String convert(String q){

       String p ="";
       int i;
       char c;

       for(i=0;i<n;i++){

        c = q.charAt(i);

        if(isOperand(c)==true){
            p = p+c;
        }

        else if(c=='(')st.push(c);

        else if(isOperator(c)==true){
           p = p + " ";
           while(precedence(st.peek())>=precedence(c)){
              p = p+" "+st.pop()+" ";


           } ///  end of while
            st.push(c);

        }  // is operator



            else if(c ==')'){

              while(st.peek()!='(')
                    p=p+ " "+st.pop()+ " ";

                    st.pop();
            }


       } /// end of For

      return p;
   } //convert

 }  /// end of postfix class

////////////////////////////////////////////////////////////////////

public class cse0208 {

    /**
     * @param args the command line arguments
     */
    public static void main(String[] args) {

        Scanner s = new Scanner(System.in);
        String p,q;
        System.out.println("Inter an Infix expression");

        q= s.nextLine();
        q= q.trim()+')';
        int total;
        total = q.length();

        Postfix pf = new Postfix(total);
        p =pf.convert(q);

         System.out.println("After Postfix Expression");
         System.out.println(p);


    }

}