How can you obtain a stream of elements from a collection as a Map using the Stream API?

In Java Stream API, you can convert a collection to a Map using the Collectors.toMap() method. You need to specify functions that extract the key and value from the stream elements.

Example: there is a list of Person objects, and you want to get a Map where the key is the ID, and the value is the name.

import java.util.*;
import java.util.stream.*;

class Person {
    private int id;
    private String name;

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

    public int getId() { return id; }
    public String getName() { return name; }
}

public class Example {
    public static void main(String[] args) {
        List<Person> people = Arrays.asList(
            new Person(1, "Alice"),
            new Person(2, "Bob"),
            new Person(3, "Charlie")
        );

        Map<Integer, String> idToName = people.stream()
            .collect(Collectors.toMap(Person::getId, Person::getName));

        System.out.println(idToName);
    }
}

The result will be a Map with keys as IDs and values as names.