How to Concatenate Two Arrays in Java?

How can I concatenate two String arrays in Java?

void f(String[] first, String[] second) {
    String[] both = ???
}

Concatenating two String arrays in Java can be accomplished using various methods, each with its own advantages. In this guide, we will explore the most straightforward and efficient approaches to achieve this, including using the built-in System.arraycopy(), the Arrays class, and modern Java Streams.

import java.util.Arrays;

public class ArrayConcat {
    public static void concatenateArrays(String[] first, String[] second) {
        String[] both = new String[first.length + second.length];
        System.arraycopy(first, 0, both, 0, first.length);
        System.arraycopy(second, 0, both, first.length, second.length);
        System.out.println(Arrays.toString(both));
    }
}

Causes

• Inefficient concatenation can lead to performance issues in large applications.
• Not using the right method can result in unnecessary memory consumption.

Solutions

• Using System.arraycopy() for optimized performance.
• Using the Arrays class to concatenate arrays gracefully.
• Utilizing Java Streams for cleaner, functional-style code.

Mistake: Not initializing the new array with the correct length.

Solution: Make sure to set the length of the new array to the sum of both original arrays.

Mistake: Using a loop instead of array copy functions, which is less efficient.

Solution: Use System.arraycopy() for efficiency when concatenating arrays.