Answer by gustafc for What is more efficient: System.arraycopy or Arrays.copyOf?

If you want an exact copy of an array (say, if you want to do a defensive copy), the most effective way of copying an array is probably using the array object's clone() method:

class C {
    private int[] arr;
    public C(int[] values){
        this.arr = values.clone();
    }
}

I haven't bothered to test the performance of it, but it stands a good chance to be pretty fast since it's all native (allocation and copying in call), and cloning is kind of a special JVM blessed way of copying objects (and it's mostly evil for other purposes) and is likely to be able to take some "shortcuts".

Personally, I'd still use clone if it was slower than any other way of copying, because it's easier to read and nigh-impossible to screw up when writing. System.arrayCopy, on the other hand...