Shallow vs Deep copy in Java
When creating copies of arrays or objects one can make a deep copy or a shallow copy.
Shallow Copy
import java.util.Arrays;
public class ShallowAndDeep2 {
public static void main(String[] args) {
int[] arr1 = { 1, 2, 3, 4, 5, 6 };
// Printing array elements
System.out.println("arr1 : " + Arrays.toString(arr1));
int[] arr2 = arr1; // Shallow Copy, both arrays points to same memory locations
// one value of array2 changed, but while both array points to same location, values of arr1 are also same
arr2[2] = 10;
System.out.println("arr2 : " + Arrays.toString(arr2));
System.out.println("arr1 again : " + Arrays.toString(arr1));
}
}
Output
arr1 : [1, 2, 3, 4, 5, 6] arr2 : [1, 2, 10, 4, 5, 6] arr1 again : [1, 2, 10, 4, 5, 6]
In above example we have changed the value of arr1[2] to 10. Since it’s a shallow copy so corresponding arr1 values are also changed.
Deep Copy
import java.util.Arrays;
public class ShallowAndDeep2 {
public static void main(String[] args) {
int[] arr1 = { 1, 2, 3, 4, 5, 6 };
// Printing array elements
System.out.println("arr1 : " + Arrays.toString(arr1));
int[] arr2 = new int[arr1.length];
// Deep copy, copying elements one by one
for (int a = 0; a < arr1.length; a++)
arr2[a] = arr1[a];
// one value of array2 changed, and only value for arr1 will be changed
// values of arr1 and arr2 are not same
arr2[2] = 10;
System.out.println("arr2 : " + Arrays.toString(arr2));
System.out.println("arr1 again : " + Arrays.toString(arr1));
}
}
Output
arr1 : [1, 2, 3, 4, 5, 6] arr2 : [1, 2, 10, 4, 5, 6] arr1 again : [1, 2, 3, 4, 5, 6]
