How do I copy an array?

Question

What I'm trying to do is I'm trying to take an image and make it a tiled image. The starting image should look like this. http://i1146.photobucket.com/albums/o525/walroid/letter_Q_grayscale_zpsd3b567a7.jpg And then what the image is turned into tiles then it should look like this: http://i1146.photobucket.com/albums/o525/walroid/replicate_example_zps5e5248e8.jpg In my code the pictures are saved into an array which is called into the method. What I want to do is copy that array and then put it into another array which will replicate the image. How do I do that? Here's my entire code:

import java.awt.Color;
import java.awt.image.BufferedImage;
import java.io.*;
import javax.imageio.ImageIO;

public class ImageProcessor {
    public static void main(String[] args) {


        if (args.length < 3) {
            System.out.println("Not enough arguments");
            System.exit(-1);
        }
        String function = args[0];
        if (function.equals("-reflectV")) {
            String inputFileName = args[1];
            String outputFileName = args[2];

            int[][] imageArr = readGrayscaleImage(inputFileName);
            int[][] reflectedArr = reflectV(imageArr);

            writeGrayscaleImage(outputFileName, reflectedArr);
        } else if (function.equals("-reflectH")) {
            String inputFileName = args[1];
            String outputFileName = args[2];

            int[][] imageArr = readGrayscaleImage(inputFileName);
            int[][] reflectedArr = reflectH(imageArr);

            writeGrayscaleImage(outputFileName, reflectedArr);
        } else if (function.equals("-ascii")) {
            String inputFileName = args[1];
            String outputFileName = args[2];

            int[][] imageArr = readGrayscaleImage(inputFileName);
            int[][] reflectedArr = reflectV(imageArr);
            try {
                PrintStream output = new PrintStream(new File("output.txt"));
            } catch (java.io.FileNotFoundException ex) {
                System.out.println("Error: File Not Found");
                System.exit(-1);
            }
        } else if (function.equals("-adjustBrightness")) {
            String amount = args[1];
            int a = Integer.parseInt(amount);
            System.out.print(a)

            String inputFileName = args[1];
            String outputFileName = args[2];

            int[][] imageArr = readGrayscaleImage(inputFileName);
            int[][] brightnessArr = adjustBrightness(imageArr);

            writeGrayscaleImage(outputFileName, brightnessArr);

        } else
            System.out.println("That is not a valid choice");
        system.exit(-1)


        public static int[][] reflectV ( int[][] arr){
            int[][] reflected = new int[arr.length][arr[0].length];
            for (int i = 0; i < arr.length; i++) {
                for (int j = 0; j < arr[i].length; j++) {
                    reflected[i][j] = arr[i][arr[i].length - 1 - j];
                }
            }

            return reflected;
        }

        public static int[][] reflectH ( int[][] arr){
            int[][] reflected = new int[arr.length][arr[0].length];
            for (int i = 0; i < arr.length; i++) {
                for (int j = 0; j < arr[i].length; j++) {
                    reflected[j][i] = arr[i][arr[j].length - 1 - j];
                }
            }

            return reflected;
        }

        public static int[][] adjustBrightness ( int[][] arr){
            int[][] brightness = new int[arr.length][arr[0].length];
            for (int i = 0; i < arr.length; i++) {
                for (int j = 0; j < arr[i].length; j++) {
                    RGB
                }
            }

            return brightness;
        }

        public static int[][] readGrayscaleImage (String filename){
            int[][] result = null; //create the array
            try {
                File imageFile = new File(filename);    //create the file
                BufferedImage image = ImageIO.read(imageFile);
                int height = image.getHeight();
                int width = image.getWidth();
                result = new int[height][width];        //read each pixel value
                for (int x = 0; x < width; x++) {
                    for (int y = 0; y < height; y++) {
                        int rgb = image.getRGB(x, y);
                        result[y][x] = rgb & 0xff;
                    }
                }
            } catch (IOException ioe) {
                System.err.println("Problems reading file named " + filename);
                System.exit(-1);
            }
            return result;
        }


    public static void writeGrayscaleImage(String filename, int[][] array) {
        int width = array[0].length;
        int height = array.length;

        try {
            BufferedImage image = new BufferedImage(width, height,
                    BufferedImage.TYPE_INT_RGB);    //create the image

            //set all its pixel values based on values in the input array
            for (int x = 0; x < width; x++) {
                for (int y = 0; y < height; y++) {
                    int rgb = array[y][x];
                    rgb |= rgb << 8;
                    rgb |= rgb << 16;
                    image.setRGB(x, y, rgb);
                }
            }

            //write the image to a file
            File imageFile = new File(filename);
            ImageIO.write(image, "jpg", imageFile);
        } catch (IOException ioe) {
            System.err.println("Problems writing file named " + filename);
            System.exit(-1);
        }
    }
}

Answer 1

You need to do a "deep copy" of the array. Simply copying your array to a new variable will only assign the reference (shallow copy), and if you manipulate data in one of the arrays, it will change both.

Shallow Copy:

String[] myArray2 = myArray1;

This will essentially have 2 references pointing at the same data. If you change anything in myArray2, it will also change in myArray1.

Deep Copy:

There are multiple ways to do a deep copy. The obvious way is to iterate over your array and copy each element one at a time into the new array.

String[] myArray2 = new String[myArray1.length];
for (int i = 0; i < myArray1.length; i++) {

    myArray2[i] = myArray1[i];

}

A sometimes simpler/faster way is to serialize your array and then de-serialize it while it's still in memory. This causes the JVM to treat the de-serialized array as an entirely new array ("no strings attached" so-to-speak).

Here's an example from an old project of mine:

/**
 * Clones an object creating a brand new
 * object by value of input object. Accomplishes this
 * by serializing the object, then deservializing it.
 * 
 * @param obj Input Object to clone
 * @return a new List<Product> type cloned from original.
 * @throws IOException If IOException
 * @throws ClassNotFoundException If ClassNotFoundException
 */
private static List<Product> cloneProdList(Object obj) throws IOException, ClassNotFoundException {

    java.io.ByteArrayOutputStream bos = new java.io.ByteArrayOutputStream();
    java.io.ObjectOutputStream obj_out = new java.io.ObjectOutputStream(bos);
    obj_out.writeObject(obj);

    java.io.ByteArrayInputStream bis = new java.io.ByteArrayInputStream(bos.toByteArray());
    java.io.ObjectInputStream obj_in = new java.io.ObjectInputStream(bis);

    @SuppressWarnings("unchecked")
    List<Product> newObj = (List<Product>)obj_in.readObject();

    bos.close();
    bis.close();
    obj_out.close();
    obj_in.close();

    return newObj;
}

This code takes a List type as the input (well, it actually casts to an Object type), serializes and then de-serializes while still in memory, then casts back into a List object and returns the new object back out of the method.

You can modify it to use an Array object instead pretty easily. (an array[] type will autobox into Array for you)

Answer 2

https://docs.oracle.com/javase/7/docs/api/java/lang/System.html#arraycopy%28java.lang.Object,%20int,%20java.lang.Object,%20int,%20int%29

You can use System.arraycopy in a for loop to copy from one array to other.

Answer 3

Using the Array class and calling the static method Array.copyOf(array, array.length) is quite handy so that if myArray1 is the previous array and myArray2 is the new array then myArray2 = Array.copyOf(myArray1, myArray1.length)