Nucleotide Count in Java
Given a DNA string, compute how many times each nucleotide occurs in the string.
exercism fetch java nucleotide-count
Given a single stranded DNA string, compute how many times each nucleotide occurs in the string.
The genetic language of every living thing on the planet is DNA. DNA is a large molecule that is built from an extremely long sequence of individual elements called nucleotides. 4 types exist in DNA and these differ only slightly and can be represented as the following symbols: 'A' for adenine, 'C' for cytosine, 'G' for guanine, and 'T' thymine.
Here is an analogy:
- twigs are to birds nests as
- nucleotides are to DNA as
- legos are to lego houses as
- words are to sentences as...
Since this exercise has difficulty 5 it doesn't come with any starter implementation. This is so that you get to practice creating classes and methods which is an important part of programming in Java. It does mean that when you first try to run the tests, they won't compile. They will give you an error similar to:
path-to-exercism-dir\exercism\java\name-of-exercise\src\test\java\ExerciseClassNameTest.java:14: error: cannot find symbol ExerciseClassName exerciseClassName = new ExerciseClassName(); ^ symbol: class ExerciseClassName location: class ExerciseClassNameTest
This error occurs because the test refers to a class that hasn't been created yet (
To resolve the error you need to add a file matching the class name in the error to the
For example, for the error above you would add a file called
When you try to run the tests again you will get slightly different errors. You might get an error similar to:
constructor ExerciseClassName in class ExerciseClassName cannot be applied to given types; ExerciseClassName exerciseClassName = new ExerciseClassName("some argument"); ^ required: no arguments found: String reason: actual and formal argument lists differ in length
This error means that you need to add a constructor to your new class. If you don't add a constructor, Java will add a default one for you. This default constructor takes no arguments. So if the tests expect your class to have a constructor which takes arguments, then you need to create this constructor yourself. In the example above you could add:
That should make the error go away, though you might need to add some more code to your constructor to make the test pass!
You might also get an error similar to:
error: cannot find symbol assertEquals(expectedOutput, exerciseClassName.someMethod()); ^ symbol: method someMethod() location: variable exerciseClassName of type ExerciseClassName
This error means that you need to add a method called
someMethod to your new class.
In the example above you would add:
Make sure the return type matches what the test is expecting.
You can find out which return type it should have by looking at the type of object it's being compared to in the tests.
Or you could set your method to return some random type (e.g.
void), and run the tests again.
The new error should tell you which type it's expecting.
After having resolved these errors you should be ready to start making the tests pass!
Running the tests
You can run all the tests for an exercise by entering
$ gradle test
in your terminal.
The Calculating DNA Nucleotides_problem at Rosalind http://rosalind.info/problems/dna/
Submitting Incomplete Solutions
It's possible to submit an incomplete solution so you can see how others have completed the exercise.