I want to copy a larger array that some elements randomly removed by remove() method into the a small array.
I have used System.arraycopy() but this method copies elements respectively. Therefore some elements in the larger array don't be copied.
I want to copy the larger array's all non-removed elements into small array which has the length is equal to number of non-removed elements in larger array.
In case you are allowed to use other "system libraries", the solution is super-simple:
arraycopy() and copy smaller.length elements from larger to smallerThe point is: when you shuffle the large array, you put it into random order!
But in case you are not allowed to use "system" libraries; you "shuffle" yourself:
larger; and for each iteration, compute a random int within larger.length Afterwards, you can again use arraycopy.
import java.util.concurrent.ThreadLocalRandom; //for shuffling array
import java.util.Random; //for shuffling solution
public class BigToSmallArray {
public static void main(String[] args) {
int[] bigArray = new int[]{0,1,2,3,4,5,6,7,8,9};
int[] smallArray = new int[5];
int[] shuffledBigArray = shuffleArray(bigArray);
for(int i = 0; i < smallArray.length; i++) {
smallArray[i] = shuffledBigArray[i];
}
}
public static int[] shuffleArray(int arr[]) {
Random rnd = ThreadLocalRandom.current();
for (int i = arr.length - 1; i > 0; i--) {
int index = rnd.nextInt(i + 1);
// Simple swap
int a = arr[index];
arr[index] = arr[i];
arr[i] = a;
}
return arr;
}
}
ArrayListinstead of array, it shrinks when elements are temoved, and you will end up with a smallerArrayList. Another idea, make a stream, filter out removed elements and collect the remainig elements into a new array.