In Java, there are various ways to merge multiple arrays into one array efficiently. In this blog post, we will explore two common approaches to achieve this: the manual approach using loops and the built-in System.arraycopy() method.

Table of Contents

• Manual Approach
• System.arraycopy() Method
• Conclusion

Manual Approach

The manual approach involves using loops to iterate through each array and copy its elements into a new resulting array.

Here’s an example code snippet that demonstrates this approach:

public class ArrayMerger {
    public static int[] mergeArrays(int[]... arrays) {
        int totalLength = 0;
        for (int[] arr : arrays) {
            totalLength += arr.length;
        }

        int[] mergedArray = new int[totalLength];
        int index = 0;
        for (int[] arr : arrays) {
            for (int element : arr) {
                mergedArray[index++] = element;
            }
        }

        return mergedArray;
    }

    public static void main(String[] args) {
        int[] array1 = {1, 2, 3};
        int[] array2 = {4, 5};
        int[] array3 = {6, 7, 8, 9};

        int[] merged = mergeArrays(array1, array2, array3);
        System.out.println(Arrays.toString(merged));
    }
}

In this example, the mergeArrays() method takes in multiple arrays as varargs. It first calculates the total length of the merged array, initializes a new array with this length, and then iterates through each array, copying its elements into the merged array.

The output of the above code will be:

[1, 2, 3, 4, 5, 6, 7, 8, 9]

System.arraycopy() Method

The System.arraycopy() method is a built-in Java method that allows for efficient copying of arrays. It eliminates the need for manual iteration through each array and copying elements.

Here’s an example code snippet that demonstrates using the System.arraycopy() method to merge arrays:

public class ArrayMerger {
    public static int[] mergeArrays(int[]... arrays) {
        int totalLength = 0;
        for (int[] arr : arrays) {
            totalLength += arr.length;
        }

        int[] mergedArray = new int[totalLength];
        int index = 0;
        for (int[] arr : arrays) {
            System.arraycopy(arr, 0, mergedArray, index, arr.length);
            index += arr.length;
        }

        return mergedArray;
    }

    public static void main(String[] args) {
        int[] array1 = {1, 2, 3};
        int[] array2 = {4, 5};
        int[] array3 = {6, 7, 8, 9};

        int[] merged = mergeArrays(array1, array2, array3);
        System.out.println(Arrays.toString(merged));
    }
}

In this example, the System.arraycopy() method is used to copy each array into the merged array. The System.arraycopy() method takes in the source array, starting position in the source array, destination array, starting position in the destination array, and the length to copy.

The output of the above code will be the same as the previous example.

Conclusion

Merging multiple arrays into one array can be accomplished using a manual approach using loops or the built-in System.arraycopy() method. Both approaches are efficient and provide flexibility depending on your specific use case.

By using the mergeArrays() method provided in this blog post, you can merge any number of arrays into a single array effortlessly in Java.

#java #array-merging