Double to string Java Loop

Question

Hey so I am trying to get the GC-content of a DNA string is given by the percentage of symbols in the string that are C or G. For example, the GC-content of "AGCTATAG" is .375 or 37.5%. Here is what I came with up. I am having trouble with the calculations and returning the double as string.

public static double gcContent(String dna) {
    //TODO Implement this method
      double gcContent = 0;
      double count=0; 
      for (int i = 0; i < dna.length(); i ++) {
          if (gcContent == dna.length()){
              gcContent = (dna.length()/ 2) ;
          }
          return double.toString (gcContent); 
      }
  }

Your method always returns 0. And you must not convert to String if your method returns double. Can you please correct your example. — frifle, Oct 16 '15 at 06:34
Okay I'll leave it as a double but how can I get the correct output? — javakook, Oct 16 '15 at 06:43

score 2 · Answer 1 · answered Oct 16 '15 at 06:49

2

Your calculation doesnt make sense. You have to iterate over each char of your dna-string and compare this with your expected value char ('C' or 'G', upper and lower case?) If you want to return the result as string, you have to change the return type to String, too.

public static String gcContent(String dna) {
    //TODO Implement this method
    char c = 'C';
    char g = 'G';
      double gcContent = 0;
      double count=0; 
      for (int i = 0; i < dna.length(); i ++) {

          if (dna.charAt(i) == c || dna.charAt(i) == g){
              count++;
          }
      }
      gcContent = count / (double)dna.length();
      return String.valueOf(gcContent); 
  }

answered Oct 16 '15 at 06:49

Winusch

38
4

jep, thats it. But i would not convert to String in this method. Seperate the concern. You have a method that does the calculation - and it returns double. Then you have a UI or a report or just some simple `System.out...` - there you convert to String. – frifle Oct 16 '15 at 07:33
Yeah, it's the cleaner way to return the double-value and convert to string later, when u need it as string. But the TS wanted to "returning the double as string" :) – Winusch Oct 16 '15 at 07:49

score 1 · Answer 2 · answered Oct 16 '15 at 06:25

1

You cant call toString() in primitive type variable. You can use :

String.valueOf(gcContent)

answered Oct 16 '15 at 06:25

Rahman

3,755
3
26
43

score 0 · Answer 3 · answered Oct 16 '15 at 06:27

There are many ways to do this.

String.valueOf and Double.toString will work but gives you no control over the format.

Using a number formatter would be much more powerful as it lets you control the way the output is presented. So you can make it a decimal fraction, or a percentage.

Some reading for you:

https://docs.oracle.com/javase/tutorial/java/data/numberformat.html http://docs.oracle.com/javase/7/docs/api/java/text/DecimalFormat.html

George · Answer 4 · 2015-10-16T06:49:02.543

0

If you insist to use toString you can box the value in a Double object like this:

new Double(gcContent).toString();

Else the most apropriate way I think is to use String.format, because you can format the string. For example if you want two digits after the decimal point you have:

return String.format("%.2f", gcContent);

edited Oct 16 '15 at 06:49

answered Oct 16 '15 at 06:29

George

7,206
8
33
42

score 0 · Answer 5 · answered Oct 16 '15 at 06:32

0

I think you can use Double.toString(gcContent);

answered Oct 16 '15 at 06:32

user2063688

36
2

score 0 · Answer 6 · edited May 23 '17 at 10:28

0

This might not be best one, but I use this,

return gcContent + "";

How does this work can be see here : Java: How to concatenate Double to String and here : How does the String class override the + operator?

Also, you need to change your function's return type to String.

edited May 23 '17 at 10:28

Community

1
1

answered Oct 16 '15 at 06:34

Ghazanfar

1,419
13
21

score 0 · Answer 7 · answered Oct 21 '15 at 19:53

You need to count the C and G characters. Then you can use String.format(String, Object...) to return a formatted String. Something like,

public static String gcContent(String dna) {
    if (dna == null || dna.isEmpty()) return "0%";
    int count = 0;
    for (char ch : dna.toUpperCase().toCharArray()) {
        switch (ch) {
        case 'G': case 'C':
            count++;
        }
    }
    return String.format("%.1f%%", 100 * (count / (double) dna.length()));
}

public static void main(String[] args) {
    System.out.println(gcContent("AGCTATAG"));
}

Output is (as requested)

37.5%

Double to string Java Loop

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