Question

I’m trying to make a method that expects an array of int and two int S1 and int S2 as parameters. The integers represent the starting position and the ending position of a subarray within the parameter array. The method returns a new array that contains the elements from the starting position to the ending position.

This is what I have, but it keeps giving me this message:

Exception in thread "main" java.lang.ArrayIndexOutOfBoundsException
    at java.lang.System.arraycopy(Native Method)
    at testing.subArray(testing.java:14)
    at testing.main(testing.java:9)

Here’s the code:

public class testing{

public static void main(String args[])
{
int[] firstArray = {8,9,10,11,12,13};
subArray(firstArray, 2, 4);
}

public static void subArray(int[]originalArray, int S1, int S2)
{
int[] copy = new int[3];
System.arraycopy(originalArray, S1, copy, S2, 2);

for (int i = 0; i < copy.length; i++){
        System.out.println(copy[i]);}
}

}

Help please! 🙂

Answer 1

The method returns a new array that contains the elements from the starting position to the ending position.

At present it doesn’t return anything (it’s a void method). However, you could make use of Arrays.copyOfRange() if you wanted to make your job as easy as possible.

As to your current code, here are some hints:

1. Why are you always allocating three elements for copy? The size of the array ought to depend on S1 and S2.
2. The arguments to arraycopy() are completely wrong. Read the relevant part of the Java documentation and figure out what the correct values are.