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The release of Java 9 was a milestone in the Java ecosystem. The modular framework developed under Project Jigsaw became part of Java SE release. Another major feature was the JShell tool, which is a REPL tool for Java. Many other new features introduced with Java 9 are listed in the release notes: http://www.oracle.com/technetwork/java/javase/9all-relnotes-3704433.html.
In this recipe, we will enumerate and discuss some of the new features introduced with JDK 18.3 and 18.9 (Java 10 and 11).
The Java 10 release (JDK 18.3) started a six-month release cycle—every March and every September—and a new release numbering system. It also introduced many new features, the most significant of which (for application developers) are the following:
See the full list of Java 10's new features in the release notes: https://www.oracle.com/technetwork/java/javase/10-relnote-issues-4108729.html.
We will discuss the new features of JDK 18.9 in more detail in the next section.
We have picked a few features that we feel are the most important and useful for an application developer.
Epsilon is a so-called no-op garbage collector that basically does nothing. Its use cases include testing for performance, memory pressure, and the virtual machine interface. It also could be used for short-lived jobs or the jobs that do not consume much memory and do not require garbage collection.
We discussed this feature in more details in the recipe Understand Epsilon, a low-overhead garbage collector recipe in Chapter 11, Memory Management and Debugging.
JDK 18.9 standardizes the incubated HTTP API client introduced in JDK 9 and updated in JDK 10. Based on CompleteableFuture, it supports nonblocking requests and responses. The new implementation is asynchronous and provides a better traceable data flow.
Chapter 10, Networking, explains this feature in more detail in several recipes.
A local-variable syntax for lambda parameters has the same syntax as a local-variable-declaration using the reserved var type introduced in Java 11. See the Using local variable syntax for lambda parameters recipe in Chapter 15, The New Way of Coding with Java 10 and Java 11, for more details.
The Z Garbage Collector (ZGC) is an experimental low-latency garbage collector. Its pause times should not exceed 10 ms and there should be no more than 15% application throughput reduction compared to using the G1 collector. ZGC also lays a foundation for future features and optimizations. Linux/x64 will be the first platform to get ZGC support.
There are several additions to the standard Java API:
var s = Character.toString(50);
System.out.println(s); //prints: 2
var i = CharSequence.compare("a", "b");
System.out.println(i); //prints: -1
i = CharSequence.compare("b", "a");
System.out.println(i); //prints: 1
i = CharSequence.compare("this", "that");
System.out.println(i); //prints: 8
i = CharSequence.compare("that", "this");
System.out.println(i); //prints: -8
String s1 = "a";
String s2 = s1.repeat(3); //prints: aaa
System.out.println(s2);
String s3 = "bar".repeat(3);
System.out.println(s3); //prints: barbarbar
String s1 = "a";
System.out.println(s1.isBlank()); //false
System.out.println(s1.isEmpty()); //false
String s2 = "";
System.out.println(s2.isBlank()); //true
System.out.println(s2.isEmpty()); //true
String s3 = " ";
System.out.println(s3.isBlank()); //true
System.out.println(s3.isEmpty()); //false
String s = "l1 \nl2 \rl3 \r\nl4 ";
s.lines().forEach(System.out::print); //prints: l1 l2 l3 l4
String s = " a b ";
System.out.println("'" + s.strip() + "'"); // 'a b'
System.out.println("'" + s.stripLeading() + "'"); // 'a b '
System.out.println("'" + s.stripTrailing() + "'");// ' a b'
Path filePath = Path.of("a", "b", "c.txt");
System.out.println(filePath); //prints: a/b/c.txt
try {
filePath = Path.of(new URI("file:/a/b/c.txt"));
System.out.println(filePath); //prints: /a/b/c.txt
} catch (URISyntaxException e) {
e.printStackTrace();
}
Pattern pattern = Pattern.compile("^a.*z$");
Predicate<String> predicate = pattern.asMatchPredicate();
System.out.println(predicate.test("abbbbz")); // true
System.out.println(predicate.test("babbbz")); // false
System.out.println(predicate.test("abbbbx")); // false
There are quite a few other changes introduced in JDK 18.9:
Read the Java 11 (JDK 18.9) release notes for more details and other changes.
