1. Using System.arraycopy()

The System.arraycopy() method is a low-level method that performs a native copy of the elements from one array to another. Here’s how you can use it to concatenate two arrays:

int[] array1 = {1, 2, 3};
int[] array2 = {4, 5, 6};

int[] result = new int[array1.length + array2.length];
System.arraycopy(array1, 0, result, 0, array1.length);
System.arraycopy(array2, 0, result, array1.length, array2.length);

In the above example, we create a new array result with a length equal to the sum of the lengths of array1 and array2. Then we use System.arraycopy() twice to copy the elements from array1 and array2 into the result array.

2. Using Arrays.copyOf()

The Arrays.copyOf() method is a convenience method that simplifies the process of copying arrays. Here’s how you can use it to concatenate two arrays:

int[] array1 = {1, 2, 3};
int[] array2 = {4, 5, 6};

int[] result = Arrays.copyOf(array1, array1.length + array2.length);
System.arraycopy(array2, 0, result, array1.length, array2.length);

In this example, we use Arrays.copyOf() to create a new array result with a length equal to the sum of the lengths of array1 and array2, and copy the elements of array1 into result. Then we use System.arraycopy() to copy the elements of array2 into result, starting from the index where array1 ends.

Summary

Both System.arraycopy() and Arrays.copyOf() provide ways to concatenate two arrays in Java. While System.arraycopy() is a low-level method, Arrays.copyOf() is a more convenient method that simplifies the process. You can choose the method that suits your specific needs and coding style.

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