Question

Simple question, what’s the fastest way of copying an array of doubles in Java. I currently do this…

public static double[] clone_doubles(double[] from)
{
    double[] to = new double[from.length];
    for (int i = 0; i < from.length; i++) to[i] = from[i];
    return to;
}

which also does the allocation to avoid overflows, but if there is a quicker way I will separate the allocation from the copy.

I have looked at Arrays.copyOf() and System.arraycopy() but I’m wondering if anyone has any neat tricks.

Edit:
How about copying a double[][]?

Answer 1

Java Practices did a comparison of different copy methods on arrays of int:

Here are the results from their site:

java -cp . -Xint ArrayCopier performance 250000

Using clone: 93 ms
Using System.arraycopy: 110 ms
Using Arrays.copyOf: 187 ms
Using for loop: 422 ms

Looks to me like a tie between System.arraycopy() and clone().