What does this Constructor Do ?

[Ciwan]

Hi Guys

I have a bit of Java code and I'm trying to digest it and understand it.

Here is the code:

public class SimpleRandomCount extends RandomCount {
    /**
     * Constructor
     */
    public SimpleRandomCount(int size) {
        super(size);
    }
    
    /**
     * Randomise the array
     */
    protected void randomise() {
        
        Integer[] copy = new Integer[array().length];
        // used to indicate if elements have been used
        boolean[] used = new boolean[array().length];
        
        Arrays.fill(used,false);
        
        for (int index = 0; index < array().length; index++) {
            
            int randomIndex;
            
            do {
               randomIndex = randomIndex();
            } while (used[randomIndex]);
            copy[index] = array()[randomIndex];
            used[randomIndex] = true;
        }
        
        for (int index = 0; index < array().length; index++) {
            array()[index] = copy[index];
        }
        
    }

} // End of class SimpleRandomCount

The first bit of code that I'm trying to get my head around is this bit of the randomise() method:

Integer[] copy = new Integer[array().length];
        // used to indicate if elements have been used
        boolean[] used = new boolean[array().length];
        
        Arrays.fill(used,false);

What does the bottom line do and which array does it do it to ? cause there are two array (copy and used) initiated above that line !

I would greatly appreciate any help.

Thank You.

[JosAH]

Integer[] copy = new Integer[array().length];
        // used to indicate if elements have been used
        boolean[] used = new boolean[array().length];
        
        Arrays.fill(used,false);

What does the bottom line do and which array does it do it to ? cause there are two array (copy and used) initiated above that line !

Have you read the API documentation for the Arrays.fill( ... ) method? You should have; it fills an array (the first parameter) with the value mentioned as the second parameter, so it fills the entire array 'used' with the value 'false'. It is quite useless because you have just created the array so it is already filled with values 'false'.

I don't know what that constructor does besides calling its superclass constructor with the same parameter value ...

kind regards,

Jos