Help

[freakinawesome]

Can someone please help me get started with this problem?

Human and all other genomes are made up of sequences of millions of chemicals, represented by
the four letters c, g, a and t. Write a Java program that accepts strings from this language
and which rejects all other strings. Thus, your program will validate ensure that strings are
indeed valid.
accccgtaggacatc (accepted)
ttcgaaxattctcca (rejected)

Thanks

[jmboley]

Without giving away too much, try looking at the Java API documentation for java.lang.String. This is actually an easy problem to solve using String's charAt() method.

Good luck!

[freakinawesome]

Ok thanks will have a go and post what I come up with

[freakinawesome]

I think I'm almost done, can't get it to print "Invalid" though. Any ideas? Thanks




import java.util.Scanner;

public class S1 {

public static void main(String args[]) {

String inString;
boolean validity = true;
Scanner input=new Scanner(System.in);
System.out.print("Please enter a string: ");
inString=input.next();


{
int i=0;

while (i < inString.length()) {
if (inString.charAt(i) == 'g' && inString.charAt(i) == 't' && inString.charAt(i) == 'c' && inString.charAt(i) == 'a')
{
validity = true;
break;
}
i++;
}
}

if(validity = true)
System.out.println("Valid");
else
System.out.println("Invalid");

}
}

[keang]

Did you read the "Before you post" link AlbertGM supplied in your other thread. If not why not and if you did why have you not posted the code using code tags?

if(validity = true)

You should never test a boolean value for true or false for a number of reasons.

• It's pointless as the value is already true of false so you can just use it. If you want to test for not true then use the NOT operator '!'.
• It's ugly and makes the code harder to read.
• It adds another place where typos can occur and you can end up assigning a value rather than testing it as you have done (Testing for equality is done with == and not =).

[Peter_B]

if (inString.charAt(i) == 'g' && inString.charAt(i) == 't' && inString.charAt(i) == 'c' && inString.charAt(i) == 'a')

Have a close look at this line - it's not doing what you think it is.