Is there an equivalent to memcpy() in Java?

Question

I have a byte[] and would like to copy it into another byte[]. Maybe I am showing my simple 'C' background here, but is there an equivalent to memcpy() on byte arrays in Java?

Answer 1

Use System.arraycopy()

System.arraycopy(sourceArray,                   sourceStartIndex,                  targetArray,                  targetStartIndex,                  length); 

Example,

String[] source = { "alpha", "beta", "gamma" }; String[] target = new String[source.length]; System.arraycopy(source, 0, target, 0, source.length); 

or use Arrays.copyOf()
Example,

target = Arrays.copyOf(source, length); 

java.util.Arrays.copyOf(byte[] source, int length) was added in JDK 1.6.

The copyOf() method uses System.arrayCopy() to make a copy of the array, but is more flexible than clone() since you can make copies of parts of an array.

Answer 2

You might try System.arraycopy or make use of array functions in the Arrays class like java.util.Arrays.copyOf. Both should give you native performance under the hood.

Arrays.copyOf is probably favourable for readability, but was only introduced in java 1.6.

 byte[] src = {1, 2, 3, 4};  byte[] dst = Arrays.copyOf(src, src.length);  System.out.println(Arrays.toString(dst));