Whenever I input fractions I just get back my own error message, (the error message I send as System.err.println("There was an error in your input, try again."); ) or nothing at all. I think it might be a problem with my output code but I'm not sure. I'm not having a program crash error message or system error message. The error message I'm talking about is the one I have set up in case someone does something stupid like 2/3 ++ 1/3.

import java.util.*; public class Fractioncalculator { public static void main(String[] args){ boolean quit = false; //boolean for recognition of quit command boolean error = false; String inputstr = null; Scanner sc = new Scanner(System.in); //Loop for input of problem and output of solution while(quit==false){ int iterator = 31; //iterator for reduction of end result int first_whole_int = 0; //first whole integer int firstnum = 0; //first numerator int firstdenom = 0; //first denominator int second_whole_int = 0; //second whole integer int secondnum = 0; //second numerator int seconddenom = 0; //second denominator char operator; //operator storage int cmndenom = 0; //common denominator int finalint = 0; //final integer int finalnum = 0; //final numerator int finaldenom = 0; //final denominator //Request for input System.out.println("Please enter your fractions: "); inputstr = sc.nextLine(); if(inputstr.equals("quit")){ //check if quit received quit = true; } StringTokenizer errorst = new StringTokenizer(inputstr, " "); if(errorst.countTokens()!=3){ error = true; } else { StringTokenizer st1 = new StringTokenizer(inputstr, " "); //Tokenize by spaces (First Section, Operator, Second Section) // //Section One // String first = st1.nextToken(); boolean indwhole = first.contains("/"); //boolean for checking if section one contains a fraction if(indwhole==false){ //parses first whole number if above is false first_whole_int = Integer.parseInt(first); } boolean indmixed = first.contains("_"); //boolean for checking is section one is a mixed number if(indmixed==true){ //if above is true, execute parsing of first whole integer, StringTokenizer st1_sub1 = new StringTokenizer(first, "_"); //first numerator and first denominator. String first_whole = st1_sub1.nextToken(); first_whole_int = Integer.parseInt(first_whole); String firstfractionstr = st1_sub1.nextToken(); StringTokenizer st1_sub2 = new StringTokenizer(firstfractionstr, "/"); firstnum = Integer.parseInt(st1_sub2.nextToken()); firstdenom = Integer.parseInt(st1_sub2.nextToken()); } if(indwhole==true&&indmixed==false){ //if section one is just a fraction, parse numerator and denominator StringTokenizer st1_sub2 = new StringTokenizer(first, "/ "); firstnum = Integer.parseInt(st1_sub2.nextToken()); firstdenom = Integer.parseInt(st1_sub2.nextToken()); } // //operator // String op = st1.nextToken(); operator = op.charAt(0); // //Second section // String second = st1.nextToken(); boolean indwhole2 = second.contains("/"); //boolean for checking if section two contains a fraction if(indwhole2==false){ //parses first whole number if above is false second_whole_int = Integer.parseInt(second); } boolean indmixed2 = second.contains("_"); //boolean for checking is section two is a mixed number if(indmixed2==true){ //if above is true, execute parsing of second whole integer, StringTokenizer st2_sub1 = new StringTokenizer(second, "_"); //second numerator and second denominator. String second_whole = st2_sub1.nextToken(); second_whole_int = Integer.parseInt(second_whole); String secondfractionstr = st2_sub1.nextToken(); StringTokenizer st2_sub2 = new StringTokenizer(secondfractionstr, "/"); secondnum = Integer.parseInt(st2_sub2.nextToken()); seconddenom = Integer.parseInt(st2_sub2.nextToken()); } if(indwhole2==true&&indmixed2==false){ //if section one is just a fraction, parse numerator and denominator StringTokenizer st2_sub2 = new StringTokenizer(second, "/ "); secondnum = Integer.parseInt(st2_sub2.nextToken()); seconddenom = Integer.parseInt(st2_sub2.nextToken()); } if(operator == '+'){ //function execution for if operator is addition if(firstdenom!=0 && seconddenom!=0){ cmndenom = firstdenom * seconddenom; } if(firstdenom!=0 && seconddenom==0){ cmndenom = firstdenom; } if(firstdenom==0 && seconddenom!=0){ cmndenom=seconddenom; } finalint = first_whole_int + second_whole_int; if(firstnum!=0 && secondnum!=0){ finalnum = firstnum*seconddenom + secondnum*firstdenom; } if(firstnum==0 && secondnum!=0){ finalnum=secondnum; } if(firstnum!=0 && secondnum==0){ finalnum=firstnum; } } if(operator == '-'){ finalint = first_whole_int - second_whole_int; if(firstdenom!=0 && seconddenom!=0){ cmndenom = firstdenom * seconddenom; } if(firstdenom!=0 && seconddenom==0){ cmndenom = firstdenom; } if(firstdenom==0 && seconddenom!=0){ cmndenom=seconddenom; } if(firstnum!=0 && secondnum!=0){ finalnum = firstnum*seconddenom - secondnum*firstdenom; } if(firstnum==0 && secondnum!=0){ finalnum=secondnum; } if(firstnum!=0 && secondnum==0){ finalnum=firstnum; } } if(operator == '/'){ if(first_whole_int!=0 && firstdenom!=0){ firstnum=first_whole_int*firstdenom + firstnum; } if(first_whole_int!=0 && firstdenom==0){ firstnum=first_whole_int; firstdenom=1; } if(second_whole_int!=0 && seconddenom!=0){ secondnum=second_whole_int*seconddenom + secondnum; } if(second_whole_int!=0 && seconddenom==0){ secondnum=second_whole_int; seconddenom=1; } finalnum=firstnum*seconddenom; cmndenom=firstdenom*secondnum; } if(operator=='*'){ //function execution for if operator is multiplication if(firstdenom==0){ firstnum=first_whole_int; firstdenom=1; } if(firstdenom!=0 && first_whole_int!=0){ firstnum=first_whole_int*firstdenom + firstnum; } if(seconddenom==0){ secondnum=second_whole_int; seconddenom=1; } if(seconddenom!=0 && second_whole_int!=0){ secondnum=second_whole_int*seconddenom + secondnum; } finalnum=firstnum*secondnum; cmndenom=firstdenom*seconddenom; } finaldenom = cmndenom; //nuance of code, ignore while(iterator>1){ //reduction of fraction through common dividend if(finalnum%iterator==0 && finaldenom%iterator==0){ finalnum = finalnum / iterator; finaldenom = finaldenom / iterator; iterator--; } else{ iterator--; } } while(finalnum>finaldenom){ //reduction of fraction to mixed number finalnum = finalnum - finaldenom; finalint++; } //Output //Prints are self-explanatory through blue text, and are only executed if they are possible //Outputs do not print if an error has occurred if(error=false){ if(finalint!=0 && finaldenom!=1 && finaldenom!=0 && finalint>0){ System.out.println("Mixed number form: " + finalint + "_" + finalnum + "/" + finaldenom); } if(finaldenom==0 && finalnum==0 && finalint!=0){ System.out.println("Final Number: " + finalint); } finalnum = finalnum + (finalint*finaldenom); if(finaldenom!=1 && finaldenom!=0){ System.out.println("Fraction form: " + finalnum + "/" + finaldenom); } if(finaldenom==1){ System.out.println("Final Number: " + finalnum); } } else { System.err.println("There was an error in your input, try again."); } System.out.println(); } if(quit==true){ System.out.println("Program has exited."); } } } }