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Best way to copy from one array to another [closed]

Tags:

java

arrays

When I run the following code, nothing gets copied - what am I doing wrong?

Also, is this the best/most efficient way to copy data from one array to another?

public class A {
    public static void main(String args[]) {
        int a[] = { 1, 2, 3, 4, 5, 6 };
        int b[] = new int[a.length];

        for (int i = 0; i < a.length; i++) {
            a[i] = b[i];
        }
    }
}
like image 871
hans Avatar asked Jun 30 '11 15:06

hans


2 Answers

I think your assignment is backwards:

a[i] = b[i];

should be:

b[i] = a[i];

like image 31
eldarerathis Avatar answered Sep 18 '22 13:09

eldarerathis


There are lots of solutions:

b = Arrays.copyOf(a, a.length);

Which allocates a new array, copies over the elements of a, and returns the new array.

Or

b = new int[a.length];
System.arraycopy(a, 0, b, 0, b.length);

Which copies the source array content into a destination array that you allocate yourself.

Or

b = a.clone();

which works very much like Arrays.copyOf(). See this thread.

Or the one you posted, if you reverse the direction of the assignment in the loop:

b[i] = a[i]; // NOT a[i] = b[i];
like image 154
Ted Hopp Avatar answered Sep 20 '22 13:09

Ted Hopp