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Thread: How to make calls to methods

  1. #1
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    Default How to make calls to methods

    New here, I'm a compsci student taking a java programming class. Pretty basic suff but I'm getting caught here and there wrapping my head around some stuff.

    My question right now invoves making a method that takes a single int parameter and then prints all of the positive even perfect squares less than n.
    This is what I have so far:

    public class evenSquares {
     
      public void evenSquares(int n){
        for(int j = 2; j*j <= n; j += 2)
          System.out.println(j*j);
      }
    }

    public class evenSquaresDriver {
      public static void main(String[] args){
     
        evenSquares testsquare = new evenSquares(1000);
      }
    }

    This is giving me an error that "The constructor evenSquares(int) is undefined"


  2. #2
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    Default Re: How to make calls to methods

    Ok, in your evenSquares class, you have no constructor. What you do have is a method. So when you say new evenSquares(1000);, it is looking for a constructor that accepts an int.

    So, there are a few ways to fix this with what you already have, depending on what you want to do:
    If you want to create a constructor for your evenSquares class:
    public class evenSquares {
     
      public evenSquares(int n){     //NOTICE: I took out the return type to make it a constructor
        for(int j = 2; j*j <= n; j += 2)
          System.out.println(j*j);
      }
    }

    OR

    If you want to have an evenSquares class, with an evenSquares method (poor programming habit, but it will work):
    public class evenSquaresDriver {
      public static void main(String[] args){
     
        evenSquares testsquare = new evenSquares();
        testsquare.evenSquares(1000);     //Using the empty constructor, and then calling the evenSquares(int) method
      }
    }

    You seem to not fully understand the difference between a method and a constructor. I suggest you do a little bit of reading about them to better understand how it works.
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  3. The Following User Says Thank You to aussiemcgr For This Useful Post:

    ksahakian21 (April 2nd, 2012)

  4. #3
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    Default Re: How to make calls to methods

    Another question with similiar idea.

    The method stringRoot is passed a string of digits as a paramater and returns the square root of the number represented by those digits.

      public double stringRoot(String str){
        double k = Integer.parseInt(str);
        return Math.sqrt(k);
      }

    stringRoot testDouble = new stringRoot();
    testDouble.stringRoot("1600");

    It's telling me "stringRoot cannot be resolved to a type"
    Correct me if I'm wronge but this is a method correct? I also just threw the codes into my evenSquares and evenSquaresDriver classes

  5. #4
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    Default Re: How to make calls to methods

    What class is the stringRoot(...) method in?

    You are trying to create a new Object, of type stringRoot, and calling the new Object's stringRoot(...) method, which is clearly not what you are wanting to do.
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  6. #5
    Junior Member lunix's Avatar
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    Default Re: How to make calls to methods

    ermmm, just do classname.stringRoot("1600")

    don't think you need to make an object to use a classes method?
    Feels good man

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