CODEWITHSUNDEEP
javaobjectconstructor
Jacob Burgess
Jacob Burgess

Reputation: 55

returning a value with a constructor in java

Alright So This is an Assignment, so Dont help me too much... i just need to return a DnaSequence the object. and thats it. Uhm heres the constructor

import java.io.File;
import java.lang.String;

public class DnaSequence {

  public char[] dna;

  public DnaSequence(char[] dna) {
    String str = String.valueOf(dna);
    str.replaceAll("[^ATCG]", "");
    dna = str.toCharArray();
    for (int i = 0; i < dna.length; i++) {
      this.dna[i] = dna[i];
    }
    return dna;
  }
}

I will be using io.file and lang.string later.

And here is the Main (for testing )

public class DnaSequencetEST {
  public static void main(String[] args) {
    char[] bases = { 'G', 'A', 'T', 'T', 'A', 'C', 'A' };
    DnaSequence seq = new DnaSequence(bases);
    System.out.println(seq);//Should print "GATTACA"
  }
}

And below is a link to what my finish result should do and or look like.(just for fun if you wanna look at it) http://jeff.cis.cabrillo.edu/datasets/12j_dnasequence/DnaSequence.html

So DnaSequence.java:14 error: incompatible types: unexpected return value return dna: ^ So yea Thats what ive been staring at for like 5 hours, Any help would be much appreciated

Upvotes: 0

Views: 137

Answers (3)

Miguel Gomes
Miguel Gomes

Reputation: 165

I don't know all the requirements but to pass that test you just need to implement the toString() on DnaSequence and return the DNA sequence. Note the System.out.println will always call the toString if the object passed is an Object.

Solution:

public class DnaSequence {

  public final String dna;

  public DnaSequence(char[] dna) {
    this.dna = String.valueOf(dna).replaceAll("[^ATCG]", "");
  }

  @Override
  public String toString() {
    return this.dna;
  }

}

Upvotes: 0

Elliott Frisch
Elliott Frisch

Reputation: 201447

A constructor is for initializing object internal state. Here that would logically be the char[] dna field (and don't make fields public just "because"). Next, a String is immutable; so str.replaceAll("[^ATCG]", ""); without an assignment is pointless (but you can chain it before calling to toCharArray()). You need to override toString() for the behavior you want. And you can simply pass a char[] to the String constructor. Like,

public class DnaSequence {
    private char[] dna;

    public DnaSequence(char[] dna) {
        this.dna = new String(dna).replaceAll("[^ATCG]", "").toCharArray();
    }

    @Override
    public String toString() {
        return new String(dna);
    }
}

Upvotes: 2

NiVeR
NiVeR

Reputation: 9786

Ok, two hints for you:

  • Constructors don't return values. They create objects.
  • If you want to print a custom object you should define a specfic toString method to instruct Java how should the object be displayed. Here an example.

Upvotes: 2

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