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
