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How to make elements of array immutable in Java?
No, you cannot make the elements of an array immutable.
But the unmodifiableList() method of the java.util.Collections class accepts an object of the List interface (object of implementing its class) and returns an unmodifiable form of the given object. The user has only read-only access to the obtained list.
And the asList() method of the ArrayList class accepts an array and returns a List object.
Therefore, to convert an array immutable −
Obtain the desired array.
Convert it into a list object using the asList() method.
Pass the obtained list as a parameter to the unmodifiableList() method.
Example
import java.util.Arrays;
import java.util.Collections;
import java.util.List;
public class UnmodifiableExample {
public static void main(String args[]) {
//Creating a string array
String strArray[] = {"Raju", "Rama", "Rahman", "Rachel", "Ranbhir", "Rangan"};
//Converting the string array to list object
List<String> list = Arrays.asList(strArray);
//Converting the List object to immutable
List<String> immutable = Collections.unmodifiableList(list); System.out.println(immutable);
immutable.add("komala");
}
}Output
[Raju, Rama, Rahman, Rachel, Ranbhir, Rangan] Exception in thread "main" java.lang.UnsupportedOperationException at java.util.Collections$UnmodifiableCollection.add(Unknown Source) at September19.UnmodifiableExample.main(UnmodifiableExample.java:19)
Updated on: 15-Oct-2019
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