Must be an array type but resolved to string

Question

I am getting the \"Must be an array type but it resolved to string\" error in my code. It also says that i (in the code below) cannot be resolved to a variable which I don\'

Answer 1

I think you are currently a bit weak at brackets , this is what i understood from your code and corrected it;

public class DNAcgcount{

    public double ratio(String dna){
    int count=0;
    for (int i=0;i<dna.length();i++){
        if (dna.charAt(i)== 'c')
        count+= 1;
        if (dna.charAt(i)=='g')
        count+=1;
    }
        double answer = count/(double)dna.length();
        return answer;
    }
}

After if we have to close the brackets when what you want in if is finished . I think you wanted count to be the number of time c or g is present in the dna. You also did some other mistakes like you have to use 'c' and 'g' instead of "c" and "g" if you are using .charAt(i) because it will be treated like a character and then only you can compare . You may view this link http://docs.oracle.com/javase/tutorial/java/nutsandbolts/if.html http://docs.oracle.com/javase/tutorial/java/nutsandbolts/for.html

and you may also have a look at works you can do with string like charAt.

Answer 2

Your problem is with syntax dna[i], dna is a string and you access it as it would be an array by []. Use dna.charAt(i); instead.

Answer 3

You using String incorrectly. Instead of accessing via [] use dna.charAt(i).

Altough logically a string is an array of characters in Java a String type is a class (which means it has attributes and methods) and not a typical array.

And if you want to compare a single character to another enclose it with '' instead of "":

if (dna.charAt(i) == 'c')
.
.

Answer 4

It seems like that you have a few problems with the main syntax of basic java functions like loops or if-else statement. Click here for a good tutorial on these.

You must correct your for-loop and your if-statement:

for(int i=0;i<dna.length();i++){
    if(...){
       ...;
    }
    if(...){
       ...;
    }
}

Now you wont get the Cant be resolved to a variable... exception.

Second thing is the usage of your string. You have to use it like this:

for(int i=0;i<dna.length();i++){
    if(dna.charAt(i) == 'c'){
       count += 1;
    }
    if(dna.charAt(i) == 'g'){
       count += 1;
    }
}

Now all your exceptions should be eleminated.

Answer 5

There are two errors:

count should be double or should be casted do double answer = (double)count / dna.length();

and as mentioned above you should replace dna[i] with dna.charAt(i)

Answer 6

Use {} to define the scope of the loop. Also, as others already pointed out, use charAt instead of [] and use ' for characters, and use floating point division for the ratio.

for (int i = 0; i < dna.length(); i++) {
    if (dna.charAt(i) == 'c') {
        count += 1;
    }
    if (dna.charAt(i) == 'g') {
        count += 1;
    }
}

Or a bit shorter, use || to or the two clauses together

if (dna.charAt(i) == 'c' || dna.charAt(i) == 'g') {
    count += 1;
}