adam bien's blog

Java 14 Record and Map.Entry 📎

With a Java 14+ record: 

import java.util.Map;

public record Developer(String language, int age) {
    public Developer(Map.Entry<String, Integer> entry) {
        this(entry.getKey(), entry.getValue());
    }
}
...an Map.Entry of Java's Map: 

var developers = Map.of(
            "java", 25,
            "javascript", 24,
            "ruby", 30);
...can be directly converted into a record instance: 

developers.entrySet().
            stream().
            map(Developer::new).
            forEach(System.out::println);

The snippet prints the following output:


Developer[language=java, age=25]
Developer[language=javascript, age=24]
Developer[language=ruby, age=30]

See it in action and from scratch in 3 minutes:

A Java Record can also come with additional methods / logic: 


public record Developer(String language, int age) {
    //...
    public String nicerOutput() {
        return "I'm a " + this.language() + " developer and " + this.age() + " old";
    }
}

...and used inside the stream: 


developers.entrySet().
            stream().
            map(Developer::new).
            map(Developer::nicerOutput).
            forEach(System.out::println);

The code above prints: 


I'm a javascript developer and 24 old
I'm a ruby developer and 30 old
I'm a java developer and 25 old