In this tutorial, you will learn about different ways you can use to copy arrays (both one dimensional and two-dimensional) in Java with the help of examples.<\/p>\n\n\n\n
In Java, we can copy one array into another. There are several techniques you can use to copy arrays in Java.<\/p>\n\n\n\n
Let’s take an example,<\/p>\n\n\n\n
class Main {\n public static void main(String[] args) {\n \n int [] numbers = {1, 2, 3, 4, 5, 6};\n int [] positiveNumbers = numbers; \/\/ copying arrays\n\n for (int number: positiveNumbers) {\n System.out.print(number + \", \");\n }\n }\n}<\/code><\/pre>\n\n\n\nOutput<\/strong>:<\/p>\n\n\n\n1, 2, 3, 4, 5, 6<\/samp><\/code><\/pre>\n\n\n\nIn the above example, we have used the assignment operator (=<\/code>) to copy an array named numbers<\/var> to another array named positiveNumbers<\/var>.<\/p>\n\n\n\nThis technique is the easiest one and it works as well. However, there is a problem with this technique. If we change elements of one array, corresponding elements of the other arrays also change. For example,<\/p>\n\n\n\n
class Main {\n public static void main(String[] args) {\n \n int [] numbers = {1, 2, 3, 4, 5, 6};\n int [] positiveNumbers = numbers; \/\/ copying arrays\n \n \/\/ change value of first array\n numbers[0] = -1;\n\n \/\/ printing the second array\n for (int number: positiveNumbers) {\n System.out.print(number + \", \");\n }\n }\n}<\/code><\/pre>\n\n\n\nOutput<\/strong>:<\/p>\n\n\n\n-1, 2, 3, 4, 5, 6<\/samp><\/code><\/pre>\n\n\n\nHere, we can see that we have changed one value of the numbers<\/var> array. When we print the positiveNumbers<\/var> array, we can see that the same value is also changed.<\/p>\n\n\n\nIt’s because both arrays refer to the same array object. This is because of the shallow copy. To learn more about shallow copy, visit\u00a0shallow copy.<\/p>\n\n\n\n
Now, to make new array objects while copying the arrays, we need deep copy rather than a shallow copy.<\/p>\n\n\n\n
\n\n\n\n2. Using Looping Construct to Copy Arrays<\/h2>\n\n\n\n
Let’s take an example:<\/p>\n\n\n\n
import java.util.Arrays;\n\nclass Main {\n public static void main(String[] args) {\n \n int [] source = {1, 2, 3, 4, 5, 6};\n int [] destination = new int[6];\n\n \/\/ iterate and copy elements from source to destination\n for (int i = 0; i < source.length; ++i) {\n destination[i] = source[i];\n }\n \n \/\/ converting array to string\n System.out.println(Arrays.toString(destination));\n }\n}<\/code><\/pre>\n\n\n\nOutput<\/strong>:<\/p>\n\n\n\n[1, 2, 3, 4, 5, 6]<\/code><\/pre>\n\n\n\nIn the above example, we have used the for<\/code> loop to iterate through each element of the source array. In each iteration, we are copying elements from the source<\/var> array to the destination<\/var> array.<\/p>\n\n\n\nHere, the source and destination array refer to different objects (deep copy). Hence, if elements of one array are changed, corresponding elements of another array is unchanged.<\/p>\n\n\n\n
Notice the statement,<\/p>\n\n\n\n
System.out.println(Arrays.toString(destination));<\/code><\/pre>\n\n\n\nHere, the toString() method is used to convert an array into a string. To learn more, visit the\u00a0toString() method (official Java documentation).<\/p>\n\n\n\n
\n\n\n\n3. Copying Arrays Using arraycopy() method<\/h2>\n\n\n\n
In Java, the\u00a0System class\u00a0contains a method named\u00a0arraycopy()<\/code>\u00a0to copy arrays. This method is a better approach to copy arrays than the above two.<\/p>\n\n\n\nThe arraycopy()<\/code> method allows you to copy a specified portion of the source array to the destination array. For example,<\/p>\n\n\n\narraycopy(Object src, int srcPos,Object dest, int destPos, int length)<\/code><\/pre>\n\n\n\nHere,<\/p>\n\n\n\n
- src<\/var> – source array you want to copy<\/li>
- srcPos<\/var> – starting position (index) in the source array<\/li>
- dest<\/var> – destination array where elements will be copied from the source<\/li>
- destPos<\/var> – starting position (index) in the destination array<\/li>
- length<\/var> – number of elements to copy<\/li><\/ul>\n\n\n\n
Let’s take an example:<\/p>\n\n\n\n
\/\/ To use Arrays.toString() method\nimport java.util.Arrays;\n\nclass Main {\n public static void main(String[] args) {\n int[] n1 = {2, 3, 12, 4, 12, -2};\n \n int[] n3 = new int[5];\n\n \/\/ Creating n2 array of having length of n1 array\n int[] n2 = new int[n1.length];\n \n \/\/ copying entire n1 array to n2\n System.arraycopy(n1, 0, n2, 0, n1.length);\n System.out.println(\"n2 = \" + Arrays.toString(n2)); \n \n \/\/ copying elements from index 2 on n1 array\n \/\/ copying element to index 1 of n3 array\n \/\/ 2 elements will be copied\n System.arraycopy(n1, 2, n3, 1, 2);\n System.out.println(\"n3 = \" + Arrays.toString(n3)); \n }\n}<\/code><\/pre>\n\n\n\nOutput<\/strong>:<\/p>\n\n\n\nn2 = [2, 3, 12, 4, 12, -2]\nn3 = [0, 12, 4, 0, 0]<\/samp><\/code><\/pre>\n\n\n\nIn the above example, we have used the arraycopy()<\/code> method,<\/p>\n\n\n\nSystem.arraycopy(n1, 0, n2, 0, n1.length)<\/code> – entire elements from the n1<\/var> array are copied to n2<\/var> array<\/li>System.arraycopy(n1, 2, n3, 1, 2)<\/code> – 2<\/var> elements of the n1<\/var> array starting from index 2<\/var> are copied to the index starting from 1<\/var> of the n3<\/var> array<\/li><\/ul>\n\n\n\nAs you can see, the default initial value of elements of an int<\/var> type array is 0.<\/p>\n\n\n\n
\n\n\n\n4. Copying Arrays Using copyOfRange() method<\/h2>\n\n\n\n
We can also use the copyOfRange() method defined in\u00a0Java Arrays\u00a0class to copy arrays. For example,<\/p>\n\n\n\n
\/\/ To use toString() and copyOfRange() method\nimport java.util.Arrays;\n\nclass ArraysCopy {\n public static void main(String[] args) {\n \n int[] source = {2, 3, 12, 4, 12, -2};\n \n \/\/ copying entire source array to destination\n int[] destination1 = Arrays.copyOfRange(source, 0, source.length); \n System.out.println(\"destination1 = \" + Arrays.toString(destination1)); \n \n \/\/ copying from index 2 to 5 (5 is not included) \n int[] destination2 = Arrays.copyOfRange(source, 2, 5); \n System.out.println(\"destination2 = \" + Arrays.toString(destination2)); \n }\n}<\/code><\/pre>\n\n\n\nOutput<\/strong><\/p>\n\n\n\ndestination1 = [2, 3, 12, 4, 12, -2]\ndestination2 = [12, 4, 12]<\/samp><\/code><\/pre>\n\n\n\nIn the above example, notice the line,<\/p>\n\n\n\n
int[] destination1 = Arrays.copyOfRange(source, 0, source.length);<\/code><\/pre>\n\n\n\nHere, we can see that we are creating the\u00a0destination1<\/var>\u00a0array and copying the\u00a0source<\/var>\u00a0array to it at the same time. We are not creating the\u00a0destination1<\/var>\u00a0array before calling the\u00a0copyOfRange()<\/code>\u00a0method. To learn more about the method, visit\u00a0Java copyOfRange.<\/p>\n\n\n\n
\n\n\n\n5. Copying 2d Arrays Using Loop<\/h2>\n\n\n\n
Similar to the single-dimensional array, we can also copy the 2-dimensional array using the for<\/code> loop. For example,<\/p>\n\n\n\nimport java.util.Arrays;\n\nclass Main {\n public static void main(String[] args) {\n \n int[][] source = {\n {1, 2, 3, 4}, \n {5, 6},\n {0, 2, 42, -4, 5}\n };\n\n int[][] destination = new int[source.length][];\n\n for (int i = 0; i < destination.length; ++i) {\n\n \/\/ allocating space for each row of destination array\n destination[i] = new int[source[i].length];\n\n for (int j = 0; j < destination[i].length; ++j) {\n destination[i][j] = source[i][j];\n }\n }\n \n \/\/ displaying destination array\n System.out.println(Arrays.deepToString(destination)); \n \n }\n}<\/code><\/pre>\n\n\n\nOutput<\/strong>:<\/p>\n\n\n\n[[1, 2, 3, 4], [5, 6], [0, 2, 42, -4, 5]]<\/samp><\/pre>\n\n\n\nIn the above program, notice the line,<\/p>\n\n\n\n
System.out.println(Arrays.deepToString(destination);<\/code><\/pre>\n\n\n\nHere, the\u00a0deepToString()<\/code>\u00a0method is used to provide a better representation of the 2-dimensional array. To learn more, visit\u00a0Java deepToString().<\/p>\n\n\n\n
\n\n\n\nCopying 2d Arrays using arraycopy()<\/h2>\n\n\n\n
To make the above code more simpler, we can replace the inner loop with System.arraycopy()<\/code> as in the case of a single-dimensional array. For example,<\/p>\n\n\n\nimport java.util.Arrays;\n\nclass Main {\n public static void main(String[] args) {\n \n int[][] source = {\n {1, 2, 3, 4}, \n {5, 6},\n {0, 2, 42, -4, 5}\n };\n\n int[][] destination = new int[source.length][];\n\n for (int i = 0; i < source.length; ++i) {\n\n \/\/ allocating space for each row of destination array\n destination[i] = new int[source[i].length];\n System.arraycopy(source[i], 0, destination[i], 0, destination[i].length);\n }\n \n \/\/ displaying destination array\n System.out.println(Arrays.deepToString(destination)); \n }\n}<\/code><\/pre>\n\n\n\nOutput<\/strong>:<\/p>\n\n\n\n[[1, 2, 3, 4], [5, 6], [0, 2, 42, -4, 5]]<\/samp><\/pre>\n\n\n\nHere, we can see that we get the same output by replacing the inner for<\/code> loop with the arraycopy()<\/code> method.<\/p>\n","protected":false},"excerpt":{"rendered":"In this tutorial, you will learn about different ways you can use to copy arrays (both one dimensional and two-dimensional) in Java with the help of examples. In Java, we can copy one array into another. There are several techniques you can use to copy arrays in Java. 1. Copying Arrays Using Assignment Operator Let’s […]<\/p>\n","protected":false},"author":1,"featured_media":0,"comment_status":"open","ping_status":"open","sticky":false,"template":"","format":"standard","meta":{"footnotes":""},"categories":[427],"tags":[],"_links":{"self":[{"href":"https:\/\/mudassirbackup.infinitycodestudio.com\/index.php\/wp-json\/wp\/v2\/posts\/1178"}],"collection":[{"href":"https:\/\/mudassirbackup.infinitycodestudio.com\/index.php\/wp-json\/wp\/v2\/posts"}],"about":[{"href":"https:\/\/mudassirbackup.infinitycodestudio.com\/index.php\/wp-json\/wp\/v2\/types\/post"}],"author":[{"embeddable":true,"href":"https:\/\/mudassirbackup.infinitycodestudio.com\/index.php\/wp-json\/wp\/v2\/users\/1"}],"replies":[{"embeddable":true,"href":"https:\/\/mudassirbackup.infinitycodestudio.com\/index.php\/wp-json\/wp\/v2\/comments?post=1178"}],"version-history":[{"count":0,"href":"https:\/\/mudassirbackup.infinitycodestudio.com\/index.php\/wp-json\/wp\/v2\/posts\/1178\/revisions"}],"wp:attachment":[{"href":"https:\/\/mudassirbackup.infinitycodestudio.com\/index.php\/wp-json\/wp\/v2\/media?parent=1178"}],"wp:term":[{"taxonomy":"category","embeddable":true,"href":"https:\/\/mudassirbackup.infinitycodestudio.com\/index.php\/wp-json\/wp\/v2\/categories?post=1178"},{"taxonomy":"post_tag","embeddable":true,"href":"https:\/\/mudassirbackup.infinitycodestudio.com\/index.php\/wp-json\/wp\/v2\/tags?post=1178"}],"curies":[{"name":"wp","href":"https:\/\/api.w.org\/{rel}","templated":true}]}}