Guava’s ImmutableSet Class in Java

In this post, we will talk about Guava’s ImmutableSet class in Java which has many static utility methods for creating Immutable Sets in Java.


1. ImmutableSet.of()

Guava’s ImmutableSet.of() returns an immutable set having the given elements. Guava provides seven overloaded versions of of() method, the last one with var-args for handling any number of elements as shown below:

static ImmutableSet of()
static ImmutableSet of(E element)
static ImmutableSet of(E e1, E e2)
static ImmutableSet of(E e1, E e2, E e3)
static ImmutableSet of(E e1, E e2, E e3, E e4)
static ImmutableSet of(E e1, E e2, E e3, E e4, E e5)
static ImmutableSet of(E e1, E e2, E e3, E e4, E e5, E e6, E... others)


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2. Builder

Guava also provides a builder for creating ImmutableSet instances.


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3. ImmutableSet.copyOf()

Guava’s ImmutableSet.copyOf() method returns an immutable set containing elements of the specified collection, a non-primitive array, or an iterator.


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4. ImmutableSet.contains()

Guava’s ImmutableSet.contains() method finds if the target element is present in the immutable set or not.


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5. ImmutableSet.iterator()

Guava’s ImmutableSet.iterator() method returns an unmodifiable iterator across Set’s elements.


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