Why Upgrade to Java 11? Key Features, Performance Boosts, and Migration Tips

Java8 Commercial Licensing

Since January 2019 Oracle JDK requires a commercial license for Java SE 8 updates after 8u201/202 for commercial use; the latest free version for commercial use is 8u201/202, while personal developers can use any Oracle JDK version for free.

Java11 Performance Improvement

Switching to Java 11 can yield a 16% performance improvement, partly due to JEP 307: Parallel Full GC for G1 introduced in Java 10.

Overview of Changes from Java 8 to Java 11

Note: This article lists only the most relevant changes for developers.

Compact Strings

Starting with Java 9, strings are stored as byte[] instead of char[], saving up to 50% memory for Latin‑1 characters.

Enhanced APIs

1. String enhancements (since 11)

<code>// Check if a string is blank
" ".isBlank(); // true
// Trim leading and trailing whitespace
" Hello Java11 ".strip(); // "Hello Java11"
// Trim trailing whitespace only
" Hello Java11 ".stripTrailing(); // " Hello Java11"
// Trim leading whitespace only
" Hello Java11 ".stripLeading(); // "Hello Java11 "
// Repeat a string
"Java11".repeat(3); // "Java11Java11Java11"
// Count lines in a string
"A\nB\nC".lines().count(); // 3</code>

2. Collection enhancements

Since Java 9, the JDK provides

of

and

copyOf

methods for immutable collections.

of() @since 9

copyOf() @since 10

Example 1:

<code>var list = List.of("Java", "Python", "C"); // immutable list
var copy = List.copyOf(list); // returns the same immutable list
System.out.println(list == copy); // true
var list2 = new ArrayList<String>(); // mutable list
var copy2 = List.copyOf(list2); // creates an immutable copy
System.out.println(list2 == copy2); // false</code>

Example 2:

<code>var set = Set.of("Java", "Python", "C");
var copy = Set.copyOf(set);
System.out.println(set == copy); // true
var set1 = new HashSet<String>();
var copy1 = Set.copyOf(set1);
System.out.println(set1 == copy1); // false</code>

Example 3:

<code>var map = Map.of("Java", 1, "Python", 2, "C", 3);
var copy = Map.copyOf(map);
System.out.println(map == copy); // true
var map1 = new HashMap<String, Integer>();
var copy1 = Map.copyOf(map1);
System.out.println(map1 == copy1); // false</code>

Note: Collections created with

of

or

copyOf

are immutable; attempts to modify them throw

java.lang.UnsupportedOperationException

. Duplicates are not allowed for

Set.of

and duplicate keys for

Map.of

cause

IllegalArgumentException

.

3. Stream enhancements (since 9)

Java 9 added four new Stream methods:

ofNullable(T t)

– creates an empty stream when the argument is null.

takeWhile(Predicate<? super T> predicate)

– consumes elements while the predicate is true, then stops.

dropWhile(Predicate<? super T> predicate)

– drops elements while the predicate is true, then returns the rest.

iterate

overload with a predicate to limit the stream without

limit

.

4. Optional enhancements (since 9)

stream()

– returns a stream containing the value or an empty stream.

ifPresentOrElse(Consumer<? super T> action, Runnable emptyAction)

– executes

action

if a value is present, otherwise runs

emptyAction

.

or(Supplier<? extends Optional<? extends T>> supplier)

– returns the original optional if present, otherwise the supplied optional.

5. InputStream enhancements (since 9)

<code>String text = "java";
try (var in = new ByteArrayInputStream(text.getBytes());
     var out = new ByteArrayOutputStream()) {
    in.transferTo(out);
    System.out.println(out); // java
}</code>

HTTP Client API

The new HTTP client supports synchronous and asynchronous requests.

<code>var request = HttpRequest.newBuilder()
    .uri(URI.create("https://www.baidu.com/"))
    .build();
var client = HttpClient.newHttpClient();
// Synchronous
HttpResponse<String> resp = client.send(request, HttpResponse.BodyHandlers.ofString());
System.out.println(resp.body());
// Asynchronous
CompletableFuture<HttpResponse<String>> async = client.sendAsync(request, HttpResponse.BodyHandlers.ofString());
HttpResponse<String> resp2 = async.get();
System.out.println(resp2.body());</code>

Removed Content in Java 11

com.sun.awt.AWTUtilities

sun.misc.Unsafe.defineClass (use java.lang.invoke.MethodHandles.Lookup.defineClass)

Thread.destroy() and Thread.stop(Throwable)

sun.nio.ch.disableSystemWideOverlappingFileLockCheck

sun.locale.formatasdefault

jdk.snmp module

JavaFX (removed from OpenJDK 11, still present in Oracle JDK 10)

Java Mission Control (requires separate download)

Root Certificates: Baltimore Cybertrust Code Signing CA, SECOM, AOL, Swisscom

Java EE and CORBA modules deprecated in Java 9 are removed in Java 11

Full Linux Container (Docker) Support

Java applications running in Docker containers can now respect memory and CPU limits set by cgroups, preventing performance degradation that occurred before Java 10.

Honors container memory limits

Honors container CPU availability

Honors container CPU constraints

JDK Recommendation

Since Java 11, Oracle provides only paid commercial support. Amazon Corretto, released under the GPL, is recommended as a free, long‑term support (LTS) alternative.

Corretto LTS includes performance and security updates for Corretto 8 (free until June 2023) and quarterly updates for Corretto 11 (until at least August 2024).

Download links: Corretto 8 , Corretto 11

Disclaimer

This series is compiled by the author of the microservice core component Mica, Rú Mèng Technology . Please retain the original author and cite the source when referencing or republishing.

Column Index

"Time to Upgrade to Java 11" – JDK 11 advantages and selection

"Time to Upgrade to Java 11" – Migration pitfalls

"Time to Upgrade to Java 11" – JVM parameter tuning

"Time to Upgrade to Java 11" – HTTP/2 clear text (h2c) in microservices

"Time to Upgrade to Java 11" – Solving h2c communication issues