Java Comparing char values with set char values in a while loop

Question

I need to compare char values with set char values 'g' 'c' 'a' 't'(lower and upper case), for i want only those values to be entered. I can not seem to get certain cases of my input validation working.

f in the below strings can stand for any length of string that is not characters g,c,a,t.

The string "fffffff" keeps in the loop. The string "fgf" keeps in the loop.

However, i want the strings, "fffffg" or "gfg" to exit the loop, and they are not doing so.

The actual purpose of the exercise, to take a user input of nucleotides like g,c,a,t like the one's in DNA, and convert them into the complementary string of RNA. G is complement to C and vice versa. A is complement to U(the T is replaced with U) and vice versa. So if the string is "gcat", the response for RNA should be "cgua".

import java.text.DecimalFormat;
import javax.swing.SwingUtilities;
import javax.swing.JOptionPane;
import java.util.Random;

//getting my feet wet, 1/13/2015, program is to take a strand of nucleotides, G C  A   T, for DNA and give
//the complementary RNA strand, C G  U A.
public class practiceSixty {

public static void main(String[] args){
SwingUtilities.invokeLater(new Runnable() {
     public void run() {

        String input = null;

        boolean loopControl = true;

        char nucleotide;

        while(loopControl == true)
        {
            input = JOptionPane.showInputDialog(null, " Enter the sequence of nucleotides(G,C,A and T) for DNA, no spaces ");
            for(int i = 0; i < input.length(); i++)
            {
            nucleotide = input.charAt(i);

                if(!(nucleotide == 'G' || nucleotide == 'g' || nucleotide == 'C' || nucleotide == 'c' || nucleotide == 'A' || nucleotide == 'a' || nucleotide == 'T' || nucleotide == 't' ))
                {
                 loopControl = true;
                }
                else if(nucleotide == 'G' || nucleotide == 'g' || nucleotide == 'C' || nucleotide == 'c' || nucleotide == 'A' || nucleotide == 'a' || nucleotide == 'T' || nucleotide == 't' )
                {
                loopControl = false;
                System.out.println(nucleotide);
                }
            }

         }
            JOptionPane.showMessageDialog(null, "the data you entered is " + input);

            StringBuilder dna = new StringBuilder(input);

            for(int i = 0; i < input.length(); i++)
            {
            nucleotide = input.charAt(i);

                if(nucleotide == 'G' || nucleotide == 'g' )
                {
                    dna.setCharAt(i, 'c');
                }
                else if( nucleotide == 'C' || nucleotide == 'c')
                {
                    dna.setCharAt(i, 'g');
                }
                if(nucleotide == 'A' || nucleotide == 'a')
                {
                    dna.setCharAt(i, 'u');
                }
                else if(nucleotide == 'T' || nucleotide == 't')
                {
                    dna.setCharAt(i, 'a');
                }
            }
             JOptionPane.showMessageDialog(null, "the DNA is  , " + input + "  the RNA is  " + dna);
 }
 });
 }
 }

Dawood ibn Kareem · Accepted Answer · 2015-01-14 04:47:32Z

1

You could do your check with a single regular expression, and then just use a do/while loop to keep prompting for input until the user enters something valid.

do {
    input = JOptionPane.showInputDialog(
        null, " Enter the sequence of nucleotides(G,C,A and T) for DNA, no spaces ");
} while (!input.matches("[GCATgcat]+"));

The regular expression will match any input that consists of one or more letters of the 8 shown. When you don't get a match, the loop repeats.

edited Jan 14, 2015 at 4:47

answered Jan 14, 2015 at 4:34

Dawood ibn Kareem

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1 Comment

Ro Siv Over a year ago

Thank you David Wallace. I was wary of using Regular expressions, but they seem so useful, and my book had not really introduced me to them.

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