I have a 2-d array of double numbers it's 48 by 48, I am trying to make a method that will allow the user to select a specific amount e.g. = 7 by 7 and then put that into a new 2d array.
public static double[][] amountOTP(double [][] a, int x){
a = new double[x][x];
return a;
}
thats all i have right now, this takes an 2d array as input however even though i specified x it doesn't work.
When you want to cut it ro a smaller size and copy the part of the original array, this should work:
public static double [][] cutArray (double [][] a, int newSize){
if (x > a.length)
throw new IllegalArgumentException ("Can only make array smaller");
double [][] b = new double [newSize][newSize];
for (int i = 0; i < newSize; i++){
for (int j = 0; j < newSize; j++){
b [i][j] = a [i][j];
}
}
return b;
}
The solution below considers situations in which the requested new two-dimensional array length is greater than the original in which case we simply return the original.
Example:
public static double[][] amountOTP(double [][] a, int x){
if(x > a.length) return a;
for (double[] arr : a)
if(arr.length < x)
return a;
double[][] newArray = new double[x][x];
for (int i = 0; i < x; i++)
for (int j = 0; j < x; j++)
newArray[i][j] = a[i][j];
return newArray;
}
Sorry if I'm wrong, but I'm assuming for now that you want your method to return a smaller 2d array which contains some of the values of the given array, in which case you would need to change your method to this:
public static double[][] amountOTP(double [][] a, int x) {
double[][] b = new double[x][x];
x = Math.min(x, a.length);
for(int i = 0;i < x; i++)
for(int j = 0;j < x; j++)
b[i][j] = a[i][j];
return b;
}
This should work fine but feel free to comment and inform me if I left anything out or it doesn't work; I'm here to help. Anyways, I hope this works for you. (Also, if this isn't the answer you were looking for, feel free to tell me.)
Note: This should avoid IndexOutOfBounds exceptions, so it will still work correctly if the user gives an x value bigger than the size of a. The 2d array that this method returns will just have some values of zero where it couldn't find any numbers.
a were all the same size and equal to the length of a itself, making the 2d array a square. If the OP requires it, I will edit my answer to accommodate for a matrix which is not a square.
x<a.length?x:a.length use Math.min or at least add some spaces.Math.min? x is an integer...I think it's something like that you're looking for :
public static double[][] amountOTP(double [][] a, int x){
double [][] ret = new double[x][x];
for(int i = 0; i < x; i++)
for(int j = 0; j < x; j++)
ret[i][j] = a[i][j];
return ret;
}
But you have to be careful with the parameters because it can cause an IndexOutOfBounds exception
I see you already have a lot of answers, but nobody was making use of the excellent Arrays.copyOf Java API method:
public static double[][] amountOTP(double [][] a, int x){
a = Arrays.copyOf(a, x);
for(int i=0; i<a.length; i++) {
if(a[i] != null) {
a[i] = Arrays.copyOf(a[i], x);
} else {
a[i] = new double[x]; // allows growth
}
}
return a;
}
you are actually not yet initializing the array so the method should be like this
public static void main(String[] args)
{
double[][] a=amountOTP(3);
for(int j=0;j<a.length;++j)
{
for(int i=0;i<a[j].length;++i)
{
a[j][i]=2;
}
}
for(int j=0;j<a.length;++j)
{
for(int i=0;i<a[j].length;++i)
{
System.out.println(a[j][i]);
}
}
}
public static double[][] amountOTP(int x)
{
return new double[x][x];
}
