Guava ImmutableSet.of() method in Java

In this post, we will explain what the Guava ImmutableSet.of() method does, how to use it, and what benefits it offers over other solutions. We will also provide some examples and code snippets to demonstrate its usage in different scenarios.

1. Overview of `ImmutableSet.of()` method

The Guava ImmutableSet.of() method is a static factory method that creates and returns an immutable set containing the given elements. The method has seven overloaded versions that can handle different numbers of elements. The last version uses varargs to accept any number of elements. The signature of the method is as follows:

public static <E> ImmutableSet<E> of()

public static <E> ImmutableSet<E> of(E element)

public static <E> ImmutableSet<E> of(E e1, E e2)

public static <E> ImmutableSet<E> of(E e1, E e2, E e3)

public static <E> ImmutableSet<E> of(E e1, E e2, E e3, E e4)

public static <E> ImmutableSet<E> of(E e1, E e2, E e3, E e4, E e5)

public static <E> ImmutableSet<E> of(E e1, E e2, E e3, E e4, E e5, E e6, E... others)

The return type of the method is an ImmutableSetlt;E> that represents the immutable set of elements. The method has some constraints and properties:

The elements must not be null. If any element is null, a NullPointerException will be thrown.
The elements must be distinct. If any element is duplicated, an IllegalArgumentException will be thrown.
The order of the elements in the immutable set is determined by the order of the arguments. The iteration order of the immutable set is consistent with this order.
The immutable set is guaranteed to be serializable if all its elements are serializable.
The immutable set may or may not support hashCode() and equals() methods. This depends on whether the elements support these methods or not.

2. Usage of `ImmutableSet.of()` method

To use the Guava ImmutableSet.of() method, you need to have Guava in your classpath. Then, you can import the ImmutableSet class from com.google.common.collect package and use the ImmutableSet.of() method to create an immutable set with the given elements. For example:

import com.google.common.collect.ImmutableSet;

class Main {

public static void main(String[] args) {

// Create an immutable set with three elements

ImmutableSet<String> countries = ImmutableSet.of("Canada", "USA", "Mexico");

// Create an immutable set with four elements

ImmutableSet<Integer> primes = ImmutableSet.of(2, 3, 5, 7);

// Create an immutable set with five elements

ImmutableSet<Character> vowels = ImmutableSet.of('a', 'e', 'i', 'o', 'u');

// Create an empty immutable set

ImmutableSet<String> empty = ImmutableSet.of();

}

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You can also use the varargs version of the method to create an immutable set with any number of elements. For example:

import com.google.common.collect.ImmutableSet;

class Main {

public static void main(String[] args) {

// Create an immutable set with seven elements using varargs

ImmutableSet<Integer> nums = ImmutableSet.of(1, 2, 3, 4, 5, 6, 7);

System.out.println(nums); // [1, 2, 3, 4, 5, 6, 7]

}

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3. Benefits of `ImmutableSet.of()` method

There are several benefits of using Guava ImmutableSet.of() method over other solutions for creating an immutable set:

It is concise and expressive. You don’t need to create a mutable set first and then wrap it with an unmodifiable view. You can simply call one method and pass the elements as arguments.
It is consistent and compatible. You can use it with any type of elements, as long as they are not null or duplicated. You can also use it with any methods or operations supported by the Set interface, such as contains(), size(), isEmpty(), etc.
It is safe and efficient. You don’t need to worry about the immutability of the set, as it is guaranteed by the method. The method also optimizes the memory usage and performance of the immutable set, depending on the number and type of the elements.

That’s all about Guava ImmutableSet.of() method in Java. For more information about this method, you can check out the Guava official documentation or its GitHub repository.

Guava ImmutableSet.of() method in Java

1. Overview of ImmutableSet.of() method

2. Usage of ImmutableSet.of() method

3. Benefits of ImmutableSet.of() method

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1. Overview of `ImmutableSet.of()` method

2. Usage of `ImmutableSet.of()` method

3. Benefits of `ImmutableSet.of()` method