Thread: Generic Array Tools (lend me a critical eye)

Is there a problem with this conceptually - as in do you foresee any issues?

/*
*  Trying to make a universal tool for increment an array by one while keeping all the previous values in place.
* 
*/
                public K[] increment(K[] k){
		int i = 0;
		K[] tmp = (K[])new Object[Array.getLength(k)+1]; 
/*
* Parses through the passed k and fills tmp with all of ks values
*                
*/
		for(K kk: k){
			tmp[i] = kk;
			++i;
					}
					return tmp;
				    }

Consequently then this.

/*
*  Same with the first one, but for 2D arrays.
*
*/
	public K[][] increment(K[][] k){
		int i = 0;
		int ii = 0;
		K[][] tmp = (K[][])new Object[Array.getLength(k)+1][];
		for(K[] kara: k){
 
//          instantiate a new array at i with the length of the current iteration ( kara )
 
			tmp[i] = (K[])new Object[Array.getLength(kara)];
			for(K kay: kara){
 
   //              fill tmp's array at i with the same values of kara
 
				tmp[i][ii]=kay;
				++ii;
							}
							++i;
							ii=0;
						}	
							return tmp;	
								   }

What is the code supposed to do? Add some comments describing what it does and any problems it had to solve to get it to work.

The Arrays class has methods that do some of that more efficiently.

The copy part

I'm not sure about the goal here, but if you are wishing for a more dynamic array perhaps use a List. Alternatively you can make your methods more flexible by adding a parameter which allows one to expand the array by a given value (rather than 1 every time).

Also see System (Java Platform SE 7 )

And lastly, are you looking to make a copy of the array, or reference the same (your 2D array references...and it should be noted in the comments that it does this - thus changes in the parameter array affect the returned array)

Originally Posted by KAJLogic

Can you elaborate on your lastly; where does it reference?

Consider the following - an adaptation of your 2D array code:

public static void main(String[] args){
	int[][] a = {{1,2},{3,4}};
	int[][] b = new int[a.length+1][];
	for ( int i = 0; i < a.length; i++ ){
		b[i] = a[i];
	}
 
	System.out.println(Arrays.toString(a[0]));
	System.out.println(Arrays.toString(b[0]));
	a[0][0] = 10000;
	System.out.println(Arrays.toString(a[0]));
	System.out.println(Arrays.toString(b[0]));		
}
/*
prints:
[1, 2]
[1, 2]
[10000, 2]
[10000, 2]
 
*/

Note the above code changes a value within the a array, which also changes the value in array b because b[n] references a[n] rather than copies. Whether this is the behavior you seek I do not know, but it should be explicit in the comments. You might be better off getting explicit advice (or advice for easier alternatives) to expand upon what your goal/requirement(s) actually is