Solved

Trying to check command line for bad input with while loop so if wrong it will reprompt questions

Posted on 2004-09-08
3
229 Views
Last Modified: 2012-06-27
Hello, i hope this is an easy fix here is my problem..........

I'm trying to use the commandline to prompt the user for two things the degree of polynomial and its coefficients as follows but if it makes any error i want to reprompt the questions untill they answer correctly.I'll do this with a while true loop and 2 if statements if the two statements not entered flag will be false exit while loop continue calculation

enter degree:
enter coeff with spaces betwwen each ex 1 2 3:

then i'll use string tokenizer to get each coeeficient and place into an array. My problem is io need to make sure when they enter a degree these two cases are followed countTokens is number of coeff

1) if (degree < countTokens() ) thedn reprompt questions because degree was smallerthan the amount of coeff

2) if(degree +2 <=  countTokens() this would mean the array[degree+1] would give out of boundry exception because more coefficients than array allots

does this logic make sense?  so example input output

enter degree:3
coeff :1 2
so this would re ask question

enter degree:3
coeff: 1 2 3 4 5
reask question

enter deg:3
coef 1 2 3 4
ok ! this will break the loop.


so here is my code please any help will be greatly appreciated i can't get it to only respond when appriate datra is answered to stop array exceptions.

==============code=======================

boolean poly_flag=true;

                    while(poly_flag)
                    {


                        System.out.println("Enter in degree of polynomial : ");
                        main.setDegree( Integer.parseInt(buffer.readLine()) );             //grab degree from user input


                      System.out.println("Enter in non negative coefficients n for example 1 2 3 will be 1x^2 + 2x + 3");
                    coef_input = buffer.readLine();                            //grab coefficients from user input

                      coef = new int[main.getDegree() +1];    // allocate array size of degree plus one

                       token = new StringTokenizer(coef_input); //Use stringtokenizer to truncate coefficients


               int deg = main.getDegree();
                // check to make sure coefficients do not exceed array or are smallr than degree
                if( deg >=  token.countTokens() )
                {
                              
                    System.out.println("Your degree is bigger than the amount of coefficients please try again");
                    poly_flag=true
               }
                else
       poly_flag=false;


                  }//end while loop
0
Comment
Question by:tyweed420
3 Comments
 
LVL 86

Expert Comment

by:CEHJ
Comment Utility
>>because more coefficients than array allots

Any particular reason why you should limit this?
0
 

Author Comment

by:tyweed420
Comment Utility
because i use degree +1 to allocate the array., so if thery enter more coef than array allows its wrong for the polynomial and it creates out of bounds exceptionm

is this not correct thinking
0
 
LVL 1

Accepted Solution

by:
jLasitha earned 50 total points
Comment Utility
This may be the code that you want...

import java.io.*;
import java.util.*;

public class Polynomial {
   
   
    private static String read()throws Exception{
       
        BufferedReader br = new BufferedReader( new InputStreamReader( System.in ) );
        return br.readLine();
    }

    public static void main(String[] args) {
       
        int[] aCoeff;
        do{
           
            try{
                System.out.print("Enter degree :");
                int degree = Integer.parseInt( read() );
                System.out.print("Enter coeff:");
                String coeff =   read();
               
                StringTokenizer st = new StringTokenizer( coeff );
               
                int noOfCoeff = st.countTokens();
               
                if( ( degree + 1 ) ==  noOfCoeff ){
                   
                    System.out.println("Ok! Break loop");
                    aCoeff = new int[ noOfCoeff ];
                    //Copy elements to the array
                    break;
                }
                else{
                   
                     System.out.println("Reasking...");
                }
            }catch( Exception e ){
               
                System.out.print( e.getMessage() );
            }
           
        }while(true);
    }
   
}
0

Featured Post

IT, Stop Being Called Into Every Meeting

Highfive is so simple that setting up every meeting room takes just minutes and every employee will be able to start or join a call from any room with ease. Never be called into a meeting just to get it started again. This is how video conferencing should work!

Join & Write a Comment

An old method to applying the Singleton pattern in your Java code is to check if a static instance, defined in the same class that needs to be instantiated once and only once, is null and then create a new instance; otherwise, the pre-existing insta…
Java contains several comparison operators (e.g., <, <=, >, >=, ==, !=) that allow you to compare primitive values. However, these operators cannot be used to compare the contents of objects. Interface Comparable is used to allow objects of a cl…
Viewers learn about the “for” loop and how it works in Java. By comparing it to the while loop learned before, viewers can make the transition easily. You will learn about the formatting of the for loop as we write a program that prints even numbers…
Viewers will learn about basic arrays, how to declare them, and how to use them. Introduction and definition: Declare an array and cover the syntax of declaring them: Initialize every index in the created array: Example/Features of a basic arr…

763 members asked questions and received personalized solutions in the past 7 days.

Join the community of 500,000 technology professionals and ask your questions.

Join & Ask a Question

Need Help in Real-Time?

Connect with top rated Experts

12 Experts available now in Live!

Get 1:1 Help Now