Bdtjtk

I am writing a program to delete one of the field from a tab separated input table. And I need the user to give me the position of the field which they wish to delete.

I want to keep asking for the number until it is valid so I wrote the following code (which is the code that I think caused problem):

  boolean validPos = false;

  int pos = -1;

  while(!validPos){

    System.out.print(

    "Please enter the postion of the field you want to delete: ");

    try{

      //index is 1 less than the number so - 1

      pos = ask.nextInt() - 1;

    }catch(InputMismatchException imE){

      System.err.println(imE);

      System.out.println("Please enter a valid positive integer");

    }

    if(pos <= 0){

      System.out.println("Enter number is less than 1");

    }else{

      validPos = true;

    }//ifelse

  }//while

And when I entered an invalid input when it asked,
it keeps on printing the same thing non-stop:

$ java DeleteField

Leave empty if you want to manually enter input

Please enter the name of input file: 

Leave empty if you want to show the output here

Please enter the name of the output file: 

Please enter the postion of the field you want to delete: q

java.util.InputMismatchException

Please enter a valid positive integer

Enter number is less than 1

Please enter the postion of the field you want to delete:     java.util.InputMismatchException

Please enter a valid positive integer

Enter number is less than 1

Please enter the postion of the field you want to delete:    java.util.InputMismatchException

Please enter a valid positive integer

Enter number is less than 1

Please enter the postion of the field you want to delete:  java.util.InputMismatchException

Please enter a valid positive integer

Enter number is less than 1

Please enter the postion of the field you want to delete:   java.util.InputMismatchException

.... and so on printing forever...
It seems like the code

pos = ask.nextInt() - 1;  

did not stop and asked for an input,
May I know what happened? Thanks alot



And if you want to see the full code :

//this program input a tab separated table

//and delete one of the field according to input number

//note: if input number is more than integer range it wont work



import java.io.IOException;

import java.io.FileReader;

import java.io.FileWriter;

import java.io.BufferedReader;

import java.io.PrintWriter;

import java.util.Scanner;

import java.io.File;

import java.io.InputStreamReader;

import java.util.InputMismatchException;



public class DeleteField{

  public static void main(String args) {

    BufferedReader reader = null;

    PrintWriter writer = null;

    Scanner ask = new Scanner(System.in);

    boolean standardInput = false;

    boolean standardOutput = false;

    File inFile = null;

    File outFile = null;



try{

  boolean validInFile = false;

  while(!validInFile){

    System.out.println("Leave empty if you want to manually enter input");

    System.out.print("Please enter the name of input file: ");

    String inFileString = ask.nextLine();

    inFile = new File(inFileString);

    if(inFileString.equals("")){

      standardInput = validInFile = true;

    }else if(!inFile.exists()){

      System.out.println("This file does not exists, please enter again");

    }else{

      validInFile = true;

    }//ifelse

  }//while



  boolean validOutFile = false;

  while(!validOutFile){

    System.out.println("Leave empty if you want to show the output here");

    System.out.print("Please enter the name of the output file: ");

    String outFileString = ask.nextLine();

    outFile = new File(outFileString);

    if(outFileString.equals("")){

      standardOutput = validOutFile = true;

    }else if(outFile.exists()){

      boolean validAns = false;

      while(!validAns){

        System.out.print("File already exists, override it? (y/n): ");

        String ans = ask.nextLine();

        if(ans.equals("y")){

          validAns = validOutFile = true;

        }else if(ans.equals("n")){

          standardOutput = validAns = true;

        }else{

          System.out.println("Please supply valid answer");

        }//else

      }//while

    }else{

      validOutFile = true;

    }//else

  }//while

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

  //The code I think with problem: 

  boolean validPos = false;

  int pos = -1;

  while(!validPos){

    System.out.print(

    "Please enter the postion of the field you want to delete: ");

    try{

      pos = ask.nextInt() - 1;

    }catch(InputMismatchException imE){

      System.err.println(imE);

      System.out.println("Please enter a valid positive integer");

    }

    if(pos <= 0){

      System.out.println("Enter number is less than 1");

    }else{

      validPos = true;

    }//ifelse

  }//while



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

  if(standardInput){

    reader = new BufferedReader(new InputStreamReader(System.in));

  }else{

    reader = new BufferedReader(new FileReader(inFile));

  }



  if(!standardOutput){

    writer = new PrintWriter(new FileWriter(outFile));

  }



  String currLine;

  String res = "";//result

  boolean deleted = false;

  final String NLS = System.getProperty("line.separator");

  //read linebyline from input

  //if pos == index then skip

  //else paste each words of the line into result

  while((currLine = reader.readLine()) != null){

    String currLineArray = currLine.split("t");

    for(int index = 0; index < currLineArray.length; index++){

      if(index != pos){

        res += currLineArray[index] + "t";

      }else{//if we deleted something

        deleted = true;

      }//if

    }//for

    res += NLS;

  }//while



  //output result

  if(standardOutput){

    System.out.println(res);

  }else{

    writer.write(res);

  }

  if(!deleted){

    writer.write("Note: You did not delete any field");

  }//if



}catch(IllegalArgumentException illE){

  System.err.println("Error: " + illE.getMessage());

  System.out.println(

  "Please try again with argument as inFile outFile integer");

// }catch(IOException ioE){

//   System.err.println("Error: " + ioE.getMessage());

}catch(Exception e){

  System.err.println(e);

  System.err.println("Something unforseen happened...");

}finally{

  try{

    if(reader != null) reader.close();

  }catch(IOException ioe){

    System.out.println("Error while closing file");

    System.err.println(ioe);

  }catch(Exception e){

    System.out.println(

          "Something unforeseen happened during closing file");

    System.err.println(e);

  }

  if(writer != null){

    writer.close();

    if(writer.checkError())

      System.err.println("Something went wrong with the output");

  }

}//trycatchfinally

}//main

}//class

Try using Integer.parseInt(ask.nextLine()) instead of ask.nextInt(). Scanner.nextInt method does not read the newline character when you press enter