Hey I would like to fill an array from elements from another array. For example (below) And array b should be filled with elements in this order from array b. Is there some method for this? I only know Arrays.fill ( but it's for 1 element). The table a is variable, not static !
int a[1,2,3,4];
int b[] = new int[100];
int b[] = {1,2,3,4,1,2,3,4,...}
You can use System.arraycopy() method. Which copies a source array from a specific beginning position to the destination array from the mentioned position.
e.g. copy array a 25 times to fill in b.
int[] a = {1, 2, 3, 4};
int[] b = new int[100];
for (int i = 0; i < b.length; i += a.length) {
System.arraycopy(a, 0, b, i, 4);
}
I would imagine a simple for loop that cycles through the first array and adds to the second would be a basic solution without invoking a method you might not be familiar with.
int a[1,2,3,4];
int b[] = new int[100];
int j = 0;
for (int i = 0; i < b.length; i++)
{
if(j == 4)
{
j = 0;
}
int n = a[j];
b[i] = n;
j++;
}
Or you can have it check the array length if the size of array "a" changes
int a[1,2,3,4];
int b[] = new int[100];
int j = 0;
for (int i = 0; i < b.length; i++)
{
if(j == a.length)
{
j = 0;
}
int n = a[j];
b[i] = n;
j++;
}
Here's a way to do it with Streams
int b[] = Stream.iterate(0, i -> i == a.length - 1 ? 0 : i + 1)
.limit(100)
.mapToInt(i -> a[i])
.toArray();
Stream.iterate(0, i -> i == a.length - 1 ? 0 : i + 1):
Starts with 0 as the seed and produces a stream of Integers incrementally. We reset/restart once the index reaches the end of the array.
limit(100): Limit to 100 elements as the source of the Stream is infinite.
.mapToInt(i -> a[i]): Convert the incoming Integer index to an int by getting the element at the index from array a.
.toArray(): Collect the individual elements to an int[].
You can accomplish this with a for loop and the modulus operator:
for (int i = 0; i < b.length; i ++) {
b[i] = a[i % a.length];
}
