java - Is there any reason to prefer System.arraycopy() over clone()?

Question

When copying an entire array, I've often seen people write:

int[] dest = new int[orig.length];
System.arraycopy(orig, 0, dest, 0, orig.length);

But it seems to me there is no reason to favor this over:

int[] dest = orig.clone();

They're both shallow copies anyway. Probably these folks just don't realize that clone exists. So is there any reason not to use clone?

Answer 1

• clone() makes a distinct copy of the first array with its own reference.
• System.arraycopy() uses JNI (Java Native Interface) to copy an array (or parts of it), so it is blazingly fast, as you can confirm here;
• clone() creates a new array with the same characteristics as the old array, i.e., same size, same type, and same contents. Refer to here for some examples of clone in action;
• manual copying is, well, manual copying. There isn't much to say about this method, except that many people have found it to be the most performant.
• arraynew = arrayold doesn't copy the array; it just points arraynew to the memory address of arrayold or, in other words, you are simply assigning a reference to the old array.