Collecting a Stream to an Immutable Collection in Java

// Java Program to illustrate Collecting a Stream to an
// Immutable Collection
// Pre java 10 
// Using collectingAndThen method

// Importing Collections, Collectors and Stream classes
// from java.util package
import java.util.Collections;
import java.util.stream.Collectors;
import java.util.stream.Stream;

// Main class
// PreJava10ImmutableCollections
public class GFG {

    // Main driver method
    public static void main(String[] args)
    {

        // Custom inputs integer elements in List
        var unmodifiableList
            = Stream.of(1, 2, 3, 4, 5, 6, 7, 8, 9, 10)
                  .collect(Collectors.collectingAndThen(
                      Collectors.toList(),
                      Collections::unmodifiableList));

        System.out.println(unmodifiableList);

        // Operations like this will result in an exception
        unmodifiableList.add(12);
    }
}

// Java Program to illustrate Collecting a 
// Stream to an Immutable Collection
// Pre java 10  Using Google’s Guava library

// Importing Guava library
import com.google.common.collect.ImmutableList;
// Importing classes from java.util package
import java.util.List;
import java.util.stream.IntStream;

// Main class
public class PreJava10ImmutableCollections {

    // main driver method
    public static void main(String[] args) {

        // Using the Guava Libraries
        List<Integer> someList
            = IntStream.range(0, 15).boxed().collect(
                  ImmutableList.toImmutableList());

        // Print and display the elements
        System.out.println(someList);
    }
}

// Java Program to illustrate Collecting a Stream to
// an Immutable Collection
// Post java 10
// using toUnmodifiableList() method 

// Importing classes from java.util package
import java.util.List;
import java.util.stream.Collectors;
import java.util.stream.Stream;

// Main Class
// ImmutableCollectionList
public class GFG {

    // Main driver method
    public static void main(String[] args)
    {
        // Creating Stream class object of integer type
        Stream<Integer> evenNumberStream
            = Stream.iterate(0, i -> i + 2).limit(50);

        // Creating List class object of integer type
        List<Integer> evenNumbers
            = (List<Integer>)evenNumberStream.collect(
                Collectors.toUnmodifiableList());

        // Print all elements in the List object
        System.out.println(evenNumbers);

        // These will result in
        // java.lang.UnsupportedOperationException

        evenNumbers.add(90);
        // evenNumbers.remove(1);
    }
}

// Java Program to illustrate Collecting a Stream to
// an Immutable Collection
// Post java 10
// Using toUnmodifiableMap() method 

// Importing required libraries
import java.util.ArrayList;
import java.util.List;
import java.util.Map;
import java.util.stream.Collectors;
import java.util.stream.Stream;

// Main Class
// ImmutableCollectionMap
public class GFG {

    // Main driver method
    public static void main(String[] args)
    {

        // Creating a Map from a Stream of books by
        // creating an object of List class of books type
        List<Books> libInventory = new ArrayList<Books>();

        // Adding elements to the above object created
        // Custom input entries
        libInventory.add(
            new Books(1, "Pride and Prejudice"));
        libInventory.add(new Books(2, "The Sign of Four"));
        libInventory.add(
            new Books(3, "Sense and Sensibility"));
        libInventory.add(new Books(4, "Mansfield Park"));
        libInventory.add(
            new Books(5, "The Materese Circle"));
        libInventory.add(
            new Books(6, "The Hound of Baskerville"));
        libInventory.add(new Books(7, "Goodnight Moon"));
        libInventory.add(new Books(
            8, "How many sleeps till my Birthday"));
        libInventory.add(
            new Books(9, "The Bourne Identity"));
        libInventory.add(new Books(10, "Murder She Wrote"));
        libInventory.add(new Books(
            11, "The adventures of Hercule Poirot"));
        libInventory.add(
            new Books(12, "The song of Ice and Fire"));

        // Creating a Map class object
        // Declaring object of integer and string type
        Map<Integer, String> unmutableInventory
            = libInventory.stream().collect(
                Collectors.toUnmodifiableMap(
                    Books::getBookNumber,
                    Books::getBookName));

        // Print all the elements in the Map object created
        // above
        System.out.println(unmutableInventory);

        // This will result in an Exception
        unmutableInventory.put(13, "Some book");
    }
}

// Java Program to illustrate Collecting a Stream to
// an Immutable Collection
// Post java 10
// Using toUnmodifiableSet() method 

// Importing required libraries
import java.util.Set;
import java.util.stream.Collectors;
import java.util.stream.Stream;

// Main class
// ImmutableCollectionSet
public class GFG {

    // Main driver method
    public static void main(String[] args)
    {
        // Creating Stream object of type Double
        Stream<Double> randomDecimals
            = Stream.generate(Math::random).limit(30);

        // Now creating Set class object of type Double
        Set<Double> randomSet = randomDecimals.collect(
            Collectors.toUnmodifiableSet());

        // Print and display elements in Set object
        System.out.println(randomSet);

        // This will produce an exception
        randomSet.add(100.0);
    }
}