CODEWITHSUNDEEP
javaconstructor
Shelvacu
Shelvacu

Reputation: 4360

Java custom optional values for constructor

This code is pretty much what I want to do:

import java.util.Random;    

public class TestClass {
  protected int testVarA;
  protected int testVarB;

  public TestClass() {
    Random r = new Random();
    this(r.nextInt(),r.nextInt());
  }

  public TestClass(int testVarA, int testVarB) {
    this.testVarA = startTestVarA;
    this.testVarB = startTestVarB;
  }
}

However, this doesn't compile, since the this() statement has to be at the beggining of the function. I could do something like

this((new Random()).getNextInt(),(new Random()).getNextInt())

But that feels very improper. What is the proper way of doing this?

Upvotes: 3

Views: 57

Answers (4)

COLINHY
COLINHY

Reputation: 395

Besides the Random object, you did not define startTestVarA and startTestVarB.

Upvotes: 1

dimoniy
dimoniy

Reputation: 5995

You can use move you complex initialization logic to a separate method:

  public TestClass() {
    Random r = new Random();
    init(r.nextInt(),r.nextInt());
  }

  public TestClass(int testVarA, int testVarB) {
    init(testVarA, testVarB)
  }

  private void init(int testVarA, int testVarB) {
    this.testVarA = startTestVarA;
    this.testVarB = startTestVarB;
  }

This is more generic solution than just having Random as a field. Random field works in this particular case since all of the instances of the class can share it without any side-effects, but if you wanted to have something which is not thread-safe as an initializer, this might become a problem. Not even talking about the static field not being eligible for garbage collection. EVER

Upvotes: 1

Leo
Leo

Reputation: 6580

maybe like this?

import java.util.Random;    

public class TestClass {
  protected int testVarA;
  protected int testVarB;
  private static Random r = new Random();

  public TestClass() {
    this(r.nextInt(),r.nextInt());
  }

  public TestClass(int testVarA, int testVarB) {
    this.testVarA = testVarA;
    this.testVarB = testVarB;
  }
}

Upvotes: 0

rgettman
rgettman

Reputation: 178303

I would create your Random object as a static final variable outside of any constructors, so that you can reference it in the first line of your no-arg constructor.

private static final Random r = new Random();

public TestClass() {
  this(r.nextInt(),r.nextInt());
}

This way, you only need one Random object, and it's initialized before the constructor's first line.

Upvotes: 2

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