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up vote 0 down vote favorite

How do I make a constructor to set the length of a global array?

I have already tried several ways to do it, none successful.

Example:

public Class{

    public Class(int length){
       double[] array = new double[length]; <- this is not global

       L = length;
    }

   int L;
   double[] array = new double[L]; <- this does not work
}

I need an array with a length determined by Constructor.

share|improve this question
    
docs.oracle.com/javase/tutorial/java/nutsandbolts/arrays.htm‌​l – troy_frommer Jul 8 '13 at 14:31
    
What about declaring double[] array outside of the constructor and then creating the object array = new double[length]; inside the constructor? – hax0r_n_code Jul 8 '13 at 14:33
2  
just as a marginal remark: You should not name your class Class – Marco Forberg Jul 8 '13 at 14:34
2  
I believe you should read about object oriented programming in Java, these are really basics. – sp00m Jul 8 '13 at 14:35
up vote 6 down vote

I think it's as simple as this:

public class MyClass{
    double[] array;

    public MyClass(int length){
        array = new double[length];
    }
}

I've also made the code actually compile :) You were missing some keywords etc.

If you want to access length in your code, use array.length rather than storing it redundantly in a separate field.

Also calling your class Class is a bad choice, even as an example, because it clashes with java.lang.Class.

share|improve this answer
3  
+1 for the Remark on java.lang.Class – Marco Forberg Jul 8 '13 at 14:35
up vote 0 down vote

Declare the array as member variable. Then initialize it in the constructor.

public class A{    
    private double[] array;    
    public Class(int length){
        array = new double[length];  
        L = length;
    }    
}

You could initialize it in second way. But then you need to use a fixed length

public class A{    
    private double[] array = new double[100];  // use fixed length  
    public Class(int length){
        array = new double[length];   
        L = length;
    }    
}
share|improve this answer
up vote 0 down vote

I don't know what you are trying to achieve but why you don't simply do it this way:

public class Class{
    public Class(int length){
        this.array = new double[length]; // <- this is not global
    }
    double[] array;
}
share|improve this answer
up vote 0 down vote

You can do it 

public  class Test  {
 double[] array;

      public Test  (int length){
          array = new double[length]; <- this is not global


}
share|improve this answer
    
Please correct the code , you have never defined a class here and also the choice of Class as classname is incorrect as it clashes with java.lang.Class ! – NINCOMPOOP Jul 8 '13 at 14:41
    
@TheNewIdiot Thankyou. Did'nt realize. – sᴜʀᴇsʜ ᴀᴛᴛᴀ Jul 8 '13 at 14:43
up vote 0 down vote 
public class aClass{
    //define the variable name here, but wait to initialize it in the constructor
    public double[] array;

    public aClass(int length){
        array = new double[length];

    }

}
share|improve this answer

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