JavaStream converts List to Map example

Java Stream converts List to Map

Convert List to Map using Java Stream()method.toMap()The method accepts two parameters, the first parameter is a function used to extract the key of the Map, and the second parameter is a function used to extract the value of the Map.

Here is an example:

import .*;
import ;
public class Main {
    public static void main(String[] args) {
        List<Person> people = (
                new Person("Alice", 25),
                new Person("Bob", 30),
                new Person("Charlie", 35)
        );
        Map<String, Integer> ageByName = ()
                .collect((Person::getName, Person::getAge));
        (ageByName);
    }
}
class Person {
    private String name;
    private int age;
    public Person(String name, int age) {
         = name;
         = age;
    }
    public String getName() {
        return name;
    }
    public int getAge() {
        return age;
    }
}

In the example above, we have aPersonClass represents personnel information, including name and age. We'll have oneList<Person>Convert to oneMap<String, Integer>, where name is used as key and age is used as value. usePerson::getNameAs a key extraction function,Person::getAgeExtract function as value. Finally, we print out the results.

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