Java - Infix to Postfix Conversion Complete Source Code

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Java - Infix to Postfix Conversion





I have given here the source code in Java for InFix to PostFix Conversion with the help of Stack (Last In First Out) Data Struct implementation.

 

Source Code


import java.lang.*;

import java.util.*;

import java.io.*;

 

 

class InfixConverter

{

      public static String ReadString()

      {

           try

           {

                 InputStreamReader input = new InputStreamReader(System.in);

                 BufferedReader reader = new BufferedReader(input);

                 return reader.readLine();

           }

           catch (Exception e)

           {

 

                 e.printStackTrace();

                 return "";

           }

      }

 

 

      public static int ReadInteger()

      {

           try

           {

                 InputStreamReader input = new InputStreamReader(System.in);

                 BufferedReader reader = new BufferedReader(input);

                 return Integer.parseInt(reader.readLine());

           }

           catch (Exception e)

           {

 

                 e.printStackTrace();

                 return 0;

           }

      }

     

      public static String InfixToPostfixConvert(String infixBuffer)

      {

         int priority = 0;

         String postfixBuffer = "";

 

         Stack s1 = new Stack();

 

         for (int i = 0; i < infixBuffer.length(); i++)

         {

            char ch = infixBuffer.charAt(i);

            if (ch == '+' || ch == '-' || ch == '*' || ch == '/')

            {

               // check the precedence

               if (s1.size() <= 0)

                  s1.push(ch);

               else

               {

                  Character chTop = (Character) s1.peek();

                  if (chTop == '*' || chTop == '/')

                     priority = 1;

                  else

                     priority = 0;

                  if (priority == 1)

                  {

                     if (ch == '+' || ch == '-')

                     {

                        postfixBuffer += s1.pop();

                        i--;

                     }

                     else

                     { // Same

                        postfixBuffer += s1.pop();

                        i--;

                     }

                  }

                  else

                  {

                     if (ch == '+' || ch == '-')

                     {

                        postfixBuffer += s1.pop();

                        s1.push(ch);

                     }

                     else

                        s1.push(ch);

                  }

               }

            }

            else

            {

               postfixBuffer += ch;

            }

         }

         int len = s1.size();

         for (int j = 0; j < len; j++)

            postfixBuffer += s1.pop();

         return postfixBuffer;

      }

 

 

      public static void main(String[] args)

      {

         String infixBuffer = "";

         String postfixBuffer = "";

        

         if(args.length == 1)

         {

            infixBuffer = args[0];

            postfixBuffer = InfixToPostfixConvert(infixBuffer);

            System.out.println("InFix  :\t" + infixBuffer);

            System.out.println("PostFix:\t" + postfixBuffer);

            System.out.println();

         }

         else

         {

            infixBuffer = "a+b*c";

            postfixBuffer = InfixToPostfixConvert(infixBuffer);

            System.out.println("InFix  :\t" + infixBuffer);

            System.out.println("PostFix:\t" + postfixBuffer);

            System.out.println();

           

            infixBuffer = "a+b*c/d-e";

            postfixBuffer = InfixToPostfixConvert(infixBuffer);

            System.out.println("InFix  :\t" + infixBuffer);

            System.out.println("PostFix:\t" + postfixBuffer);

            System.out.println();

           

            infixBuffer = "a+b*c/d-e+f*h/i+j-k";

            postfixBuffer = InfixToPostfixConvert(infixBuffer);

            System.out.println("InFix  :\t" + infixBuffer);

            System.out.println("PostFix:\t" + postfixBuffer);

            System.out.println();

         }

      }

}

Output