How can I concatenate two arrays in Java?

Question

How can I concatenate two arrays in Java?

I need to connect two String arrays in Java.

void f(String[] first, String[] second) {

    String[] both = ???

}

What is the most effortless approach to do this?

concatenation class java

4 years ago by Kajalsi45d

2 Answers

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**espadacoder11** · Answer 1 · 2021-05-24T10:38:36

Using Stream in Java 8:



String[] both = Stream.concat(Arrays.stream(a), Arrays.stream(b))

                      .toArray(String[]::new);

Or like this, using flatMap:



String[] both = Stream.of(a, b).flatMap(Stream::of)

                      .toArray(String[]::new);

To do this for a generic type you have to use reflection:



@SuppressWarnings("unchecked")

T[] both = Stream.concat(Arrays.stream(a), Arrays.stream(b)).toArray(

    size -> (T[]) Array.newInstance(a.getClass().getComponentType(), size));

**kshitijrana14** · Answer 2 · 2021-05-25T14:31:31

I found a one-line solution from the good old Apache Commons Lang library.
ArrayUtils.addAll(T[], T...)
Code:

String[] both = ArrayUtils.addAll(first, second);

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How can I concatenate two arrays in Java?

2 Answers

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