How do we create an immutable Set in Java 9?

Immutable static factory methodSet.of()Can provide a convenient way to createimmutable collections in Java 9.

The set instance created using theSet.of()method has the following characteristics.

• Collections returned by factory methods are usuallyimmutable. This means thatcannot add,removeorreplaceelements to the collection. Calling anymodifiermethod on a collection will throw anUnsupportedOperationException.
• If the elements in the collection aremutable, it may cause the contents of the collection to appear to change.
• You can createimmutable collectionsusing static factory methods that do not allownullelements. If you try to create a collection with null elements,NullPointerExceptionwill be thrown.
• When creating an immutable collection,duplicate elementswill be rejected. Passing duplicate elements to a static factory method results in anIllegalArgumentException.
• The iteration order of collection elements isunspecifiedand may change. The Chinese translation of

Grammar

Set.of(E... elements)

Example

Example

import java.util.Set; public class SetOfMethodTest { public static void main(String args[]) { Set names = Set.of("Adithya", "Bhavish", "Chaitanya", "Jai"); System.out.println("Names - " + names); names.add("Raja"); // throws UnsupportedOperationException } }

Output

Names - [Bhavish, Adithya, Jai, Chaitanya] Exception in thread "main" java.lang.UnsupportedOperationException at java.base/java.util.ImmutableCollections.uoe(Unknown Source) at java.base/java.util.ImmutableCollections$AbstractImmutableSet.add(Unknown Source) at SetOfMethodTest.main(SetOfMethodTest.java:8)

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