creating a "reset to original values" method for an array (beginning java)

Question

I'm working on a method that carries out a variety of tasks for an array of integers. The methods include things like shifting all the elements to the right, swapping the first and last, and replacing elements with 0. I was able to successfully create methods for all of those things, but I would like to create a method that essentially 'resets' the array to its original values so I can test each of the other methods from the same set of numbers.

In other words:

prints: The original array is: 1, 2, 3

prints with swap method I made: The array with the first and last numbers swapped is: 3, 2, 1

array.reset()

prints with add method I made: The array with 6 & 7 added to the end is: 1, 2, 3, 6, 7

Here is the beginning of my method with my first attempt at a 'reset' method. I'm a bit lost as to how to set it up since everything I tried produced an error and I just seemed to be going in circles for such a ~seemingly~ simple method. Any ideas?

public class Ex2 {
private int[] values;
public Ex2(int [] initialValues) {values = initialValues;}

public void reset(){
    int[] values = values??;
}

user439793 · Accepted Answer · 2013-12-06 02:00:30Z

2

You need to make a copy of the source array. Please note that this method works for primitive arrays, but for arrays of non-primitives, you will need to use System.arrayCopy() instead.

public class Ex2 {
  private int[] values;
  private int[] savedState;
  public Ex2(int [] initialValues) {
    values = initialValues;
    savedState = initialValues.clone();
  }

  public void reset(){
    values = savedState.clone();
  }
}

answered Dec 6, 2013 at 2:00

user439793

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Comments

Pan Long · Accepted Answer · 2013-12-06 01:59:23Z

0

You can make a copy of initialValues in your constructor. the code would be look like this:

public class Ex2 {
    private int[] values;
    private int[] originValues;

    public Ex2(int [] initialValues) {
        values = initialValues;
        System.arraycopy(values, 0, originValues, 0, values.length);
    }

    public void reset(){
        System.arraycopy(originValues, 0, values, 0, originValues.length);
    }
}

edited Dec 6, 2013 at 1:59

answered Dec 6, 2013 at 1:48

Pan Long

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2 Comments

user439793 Over a year ago

Arrays are references: this will not work. You are accessing the same array using two different references.

Pan Long Over a year ago

@JohnGaughan thanks for pointing out my mistake :) then we can use array copy to do this.

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