Java 8 Sort Example

Welcome to the Java 8 tutorial for sorting an array!

First let’s define our testing variable for this tutorial:

final List<String> names = Arrays.asList(
    "John Lennon",
    "Paul McCartney",
    "George Harrison",
    "Ringo Starr");

Now that we have defined our variables, we can sort them and print them all to the console.

Java 7

If we were working in Java 7 or any older version of Java before 8, we would do this:

Collections.sort(names, new Comparator<String>() {
    @Override
    public int compare(String a, String b) {
        return a.compareTo(b);
    }
});

for (final String name : names) {
    System.out.println(name);
}

This is not so bad, but we know we can do it better in Java 8.

Java 8

We start working with the Java 7 example above and continue with removing the unnecessary anonymous inner class definition, that is not needed in Java 8:

Collections.sort(names, (String a, String b) -> {
    return a.compareTo(b);
});

Then we also can remove the method definition like this:

Collections.sort(names, (String a, String b) -> a.compareTo(b));

And Java 8 does not require method parameter types definition:

Collections.sort(names, (a, b) -> a.compareTo(b));

This is great! Now comes a real great feature of Java 8, that is called a method reference:

Collections.sort(names, String::compareTo);

That was a huge step forward! But as we will see, Java 8 offers us even a better way!

and finally…

We use the sort method on the array object itself:

names.sort(String::compareTo);

Can we use the same principle for printing?

Sure, we use for each loop on the array object, together with a method reference, that we already know:

names.forEach(System.out::println);

Java.PS

Java 8 Sort Example

Java 7

Java 8

and finally…

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