Java Concatenate Arrays

There are many ways in which you can concatenate two or more arrays in Java.

To concatenate arrays, you can use a looping statement, iterate over elements of the arrays and create a new array containing all the elements of input arrays. Or you can use ArrayUtils of apache commons library and concatenate arrays. Or you can also use Arrays class and its methods like copyOf(), to concatenate arrays.

In this tutorial, we will go through each of the above said process and write Java programs to demonstrate how we can concatenate arrays.

Example 1 – Concatenate Arrays – For Loop and Array Traversing

In the following program, we take two arrays, traverse them using Java For Loop, and create a new array with all the elements from these two input arrays. The resulting array will have a length equal to the sum of lengths of the two input arrays.

Java Program

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/**
 * Java Example Program, to Concatenate Arrays
 */
public class ConcatenateArrays {
	public static void main(String[] args) {
		//two arrays
		int[] arr1 = {1, 4, 9};
		int[] arr2 = {16, 25, 36};
		
		//concatenate arrays
		int[] result = new int[arr1.length+arr2.length];
		for(int i=0;i<arr1.length;i++) {
			result[i] = arr1[i];
		}
		for(int i=0;i<arr2.length;i++) {
			result[arr1.length+i] = arr2[i];
		}
		
		//print the result
		for(int element: result) System.out.println(element);
	}
}

Output

Example 2 – Concatenate Arrays – ArrayUtils.addAll()

In the following program, we will use ArrayUtils.addAll() method, to concatenate two arrays.

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import org.apache.commons.lang.ArrayUtils;

/**
 * Java Example Program, to Concatenate Arrays
 */
public class ConcatenateArrays {
	public static void main(String[] args) {
		//two arrays
		int[] arr1 = {1, 4, 9};
		int[] arr2 = {16, 25, 36};
		//concatenate arrays
		int[] result = ArrayUtils.addAll(arr1, arr2);
		
		//print the result
		for(int element: result) System.out.println(element);
	}
}

Output

Example 3 – Concatenate Arrays – Arrays.copyOf() and System.arraycopy()

In the following program, we will use Arrays.copyOf() method, and System.arraycopy() method to concatenate two arrays.

Java Program

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import java.util.Arrays;

/**
 * Java Example Program, to Concatenate Arrays
 */
public class ConcatenateArrays {
	public static void main(String[] args) {
		//two arrays
		int[] arr1 = {1, 4, 9};
		int[] arr2 = {16, 25, 36};
		int[] result = Arrays.copyOf(arr1, arr1.length + arr2.length);
		System.arraycopy(arr2, 0, result, arr1.length, arr2.length);
		
		//print the result
		for(int element: result) System.out.println(element);
	}
}

Output

Conclusion

In this Java Tutorial, we learned how to concatenate arrays in Java, with the help of example programs.

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Java Concatenate Arrays