How can we find the names of students who have a specific book using Java 8 streams?

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 Explanation:

In this blog post, we'll dive into Java 8 streams and demonstrate how to filter a list of Student objects to find students who have a specific book, and then extract their names.

// Create some books and students Book book1 = new Book(1, "Book A"); Book book2 = new Book(2, "Book B"); Book book3 = new Book(3, "Book C");

List<Student> students = new ArrayList<>(); students.add(new Student(1, "Alice", Arrays.asList(book1, book2))); students.add(new Student(2, "Bob", Arrays.asList(book2, book3))); students.add(new Student(3, "Charlie", Arrays.asList(book1, book3))); students.add(new Student(4, "David", Arrays.asList(book2)));

String bookNameToSearch = "Book A";

List<String> studentNamesWithBook =

students.stream().filter( s -> s.getBooks().stream().anyMatch(b -> b.getName().equals(bookNameToSearch))) .map(Student::getName).collect(Collectors.toList());

Sample Code:

java
import java.util.ArrayList;
import java.util.Arrays;
import java.util.List;
import java.util.stream.Collectors;

class Book {
    private int id;
    private String name;

    public Book(int id, String name) {
        this.id = id;
        this.name = name;
    }

    public String getName() {
        return name;
    }
}

class Student {
    private int id;
    private String name;
    private List<Book> books;

    public Student(int id, String name, List<Book> books) {
        this.id = id;
        this.name = name;
        this.books = books;
    }

    public String getName() {
        return name;
    }

    public List<Book> getBooks() {
        return books;
    }
}

public class StudentBookSearch {
    public static void main(String[] args) {
        // Create some books and students
        Book book1 = new Book(1, "Book A");
        Book book2 = new Book(2, "Book B");
        Book book3 = new Book(3, "Book C");

        List<Student> students = new ArrayList<>();
        students.add(new Student(1, "Alice", Arrays.asList(book1, book2)));
        students.add(new Student(2, "Bob", Arrays.asList(book2, book3)));
        students.add(new Student(3, "Charlie", Arrays.asList(book1, book3)));
        students.add(new Student(4, "David", Arrays.asList(book2)));

        String bookNameToSearch = "Book A";
        
        List<String> studentNamesWithBook = students.stream().filter( 
        		s -> s.getBooks().stream().anyMatch(b -> b.getName().equals(bookNameToSearch)))
        		.map(Student::getName).collect(Collectors.toList());


        System.out.println("Students with the book '" + bookNameToSearch + "': " + studentNamesWithBook);
    }
}

Sample Output:

arduino
Students with the book 'Book A': [Alice, Charlie]