arraycopy

I know I can simply iterate from start to end and clear those cells but I was wondering if it was possible in any faster way (perhaps using JNI-ed System.arrayCopy )? If I got it right, you need to nullify an array, or a sub-range of an array containing references to objects to make them eligible for GC. And you have a regular Java array, which stores data on-heap. Answering your question, System.arrayCopy is the fastest way to null a sub-range of an array. It is worse memory-wise than Arrays.fill though, since you would have to allocate twice as much memory to hold references at worst case

I've been trying to measure the performance of the System.arrayCopy vs Arrays.copyOf in order to choose properly one of them. Just for the sake of benchmark I added manual copy as well and the result surprised me. Obviously I'm missing something really important, could you, please, tell me, what it is? The implementation is as follows (see first 4 methods). public class ArrayCopy { public static int[] createArray( int size ) { int[] array = new int[size]; Random r = new Random(); for ( int i = 0; i < size; i++ ) { array[i] = r.nextInt(); } return array; } public static int[] copyByArraysCopyOf

This question already has an answer here: Easy way to concatenate two byte arrays 12 answers I have two byte[] arrays which are of unknown length and I simply want to append one to the end of the other, i.e.: byte[] ciphertext = blah; byte[] mac = blah; byte[] out = ciphertext + mac; I have tried using arraycopy() but can't seem to get it to work. krock Using System.arraycopy() , something like the following should work: // create a destination array that is the size of the two arrays byte[] destination = new byte[ciphertext.length + mac.length]; // copy ciphertext into start of destination

I am having a final class NameAndValue . I copied an array of NameAndValue objects using System.arrayCopy() and when i changed a NameAndValue object in copied array, it gets reflected in the original array. public final class NameAndValue { public String name; public String value; public NameAndValue() { } public NameAndValue(String name,String value) { this.name = name; this.value = value; } } public class Main { public static void main(String[] args) { NameAndValue[] nv = new NameAndValue[4]; nv[0] = new NameAndValue("A", "1"); nv[1] = new NameAndValue("B", "2"); nv[2] = new NameAndValue("C"