Use method references instead of lambda expressions

Medium

---

JavaClean code

What is it?

Use method references when you notice a lambda expression that directly forwards its parameters to another method without altering them.

Why apply it?

This practice enhances readability and conciseness, making the code easier to understand and maintain by clearly indicating the method being referenced.

How to fix it?

Replace the lambda expression with a method reference using the syntax ClassName::methodName or instance::methodName.

Read more:

https://docs.oracle.com/javase/tutorial/java/javaOO/methodreferences.html

Examples

Example 1:

Positive

Correct implementation following the practice.

package org.example;

import java.util.HashMap;
import java.util.List;
import java.util.Map;
import java.util.stream.Collectors;

public final class Util {

    public static Map<String, Integer> nameCount(List<String> names) {
        return names.stream()
                .collect(Collectors.toMap(name -> name, name -> 1, Integer::sum));

    }

    public static void printNames(List<String> names) {
        names.forEach(System.out::println);
    }
}

Negative

Incorrect implementation that violates the practice.

package org.example;

import java.util.HashMap;
import java.util.List;
import java.util.Map;
import java.util.stream.Collectors;

public final class Util {

    public static Map<String, Integer> nameCount(List<String> names) {
        return names.stream()
                .collect(Collectors.toMap(name -> name, name -> 1, Integer::sum));

    }
    
    public static void printNames(List<String> names) {
        names.forEach(name -> System.out.println(name));
    }
}