Java 12 major language and API improvements

2024-08-06 2 min read Martin

Java ⑫ has been released in March 2019.

The following content is summarizing the most important changes to the Java API and the Java language introduced with Java ⑫.

For a more complete overview follow the links in the following sections referring to the official Oracle release documents.

API improvements

The following describes selected improvements of the Java API. See the Java 12 release notes.

String

Indent

var multiline = """
    Java
    12
    rocks!
    """;
assertEquals("""
       Java
       12
       rocks!
    """, multiline.indent(3));

With String::indent we can easily indent any string. With earlier Java versions we would have to use 3rd-party libraries such as Apache commons-lang or implement yourself..

Transform

var multiline = """
    Java
    12
    rocks!
    """;
assertEquals("""
    java
    12
    rocks!
    """, multiline.transform(String::toLowerCase));

With String::transform we can easily transform any string.

Files

Mismatch

Path tmpdir = Path.of(System.getProperty("java.io.tmpdir"));
Path path11 = Files.writeString(Files.createTempFile(tmpdir, "version", ".properties"), "Java 11 rocks");
Path path12 = Files.writeString(Files.createTempFile(tmpdir, "version", ".properties"), "Java 12 rocks");
long position = Files.mismatch(path11, path12);
assertEquals(6, position);

With Files.mismatch we can detect the first mismatching character while comparing two files.

NumberFormat

Get Compact Number Instance

NumberFormat format = NumberFormat
    .getCompactNumberInstance(Locale.US, NumberFormat.Style.SHORT);
String result = format.format(1_000); // "1K"

Collectors

Teeing

    double avgIncome = Stream.of(2000.0, 3000.0, 4000.0)
        .collect(Collectors
            .teeing(
                Collectors.summingDouble(v -> v),
                Collectors.counting(),
                (sum, count) -> sum / count)
        );
    assertEquals(3000.0, avgIncome);
  }
}

With Collectors.teeing we can have two collectors process a stream. The results of both collectors are then processed by a merge function.

JVM improvements

The following describes selected improvements of the Java JVM. See the Java 12 release notes.

With JEP-341, now CDS archives are built during the JDK build. CDS is already on by default as of Java ⑪.