Java language features series

  • New features in Java5
  • New features for Java6
  • New features in Java7
  • New features in Java8
  • New features in Java9
  • New features in Java10
  • New features for Java11

sequence

This article focuses on the new features of Java10

Feature list

  • 286: Local-Variable Type Inference(blockbuster)

(2)Local Variable Type Inference

  • 296: Consolidate the JDK Forest into a Single Repository
  • 304: Garbage-Collector Interface
  • 307: Parallel Full GC for G1
  • 310: Application Class-Data Sharing
  • 312: Thread-Local Handshakes
  • 313: Remove the Native-Header Generation Tool (javah)
  • 314: Additional Unicode Language-Tag Extensions
  • 316: Heap Allocation on Alternative Memory Devices
  • 317: Experimental Java-Based JIT Compiler(blockbuster)

Related: Java10 is here, and check out the new JIT compiler it shipped with

  • 319: Root Certificates

OpenJDK 10 Now Includes Root CA Certificates

  • 322: Time-Based Release Versioning

Java10 series (1) Time-based Release Versioning

Details of interpretation

Listed above are the major Features, but there are also some API updates and Enhancements (see What’s New in JDK 10 – New Features and Enhancements, for example).

Optional.orElseThrow()

/Library/Java/JavaVirtualMachines/jdk-10.jdk/Contents/Home/lib/src.zip! /java.base/java/util/Optional.java

  • The source code
    /**
     * If a value is present, returns the value, otherwise throws
     * {@code NoSuchElementException}.
     *
     * @return the non-{@code null} value described by this {@code Optional}
     * @throws NoSuchElementException if no value is present
     * @since 10
     */
    public T orElseThrow() {
        if (value == null) {
            throw new NoSuchElementException("No value present");
        }
        return value;
    }
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  • The instance
    @Test
    public void testOrElseThrow(){
        var data = List.of("a"."b"."c");
        Optional<String> optional = data.stream()
                .filter(s -> s.startsWith("z"))
                .findAny();
        String res = optional.orElseThrow();
        System.out.println(res);
    }
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Added orElseThrow to correspond to get

The output

java.util.NoSuchElementException: No value present

	at java.base/java.util.Optional.orElseThrow(Optional.java:371)
	at com.example.FeatureTest.testOrElseThrow(FeatureTest.java:19)
	at java.base/jdk.internal.reflect.NativeMethodAccessorImpl.invoke0(Native Method)
	at java.base/jdk.internal.reflect.NativeMethodAccessorImpl.invoke(NativeMethodAccessorImpl.java:62)
	at java.base/jdk.internal.reflect.DelegatingMethodAccessorImpl.invoke(DelegatingMethodAccessorImpl.java:43)
	at java.base/java.lang.reflect.Method.invoke(Method.java:564)
	at org.junit.runners.model.FrameworkMethodThe $1.runReflectiveCall(FrameworkMethod.java:50)
	at org.junit.internal.runners.model.ReflectiveCallable.run(ReflectiveCallable.java:12)
	at org.junit.runners.model.FrameworkMethod.invokeExplosively(FrameworkMethod.java:47)
	at org.junit.internal.runners.statements.InvokeMethod.evaluate(InvokeMethod.java:17)
	at org.junit.runners.ParentRunner.runLeaf(ParentRunner.java:325)
	at org.junit.runners.BlockJUnit4ClassRunner.runChild(BlockJUnit4ClassRunner.java:78)
	at org.junit.runners.BlockJUnit4ClassRunner.runChild(BlockJUnit4ClassRunner.java:57)
	at org.junit.runners.ParentRunner$3.run(ParentRunner.java:290)
	at org.junit.runners.ParentRunnerThe $1.schedule(ParentRunner.java:71)
	at org.junit.runners.ParentRunner.runChildren(ParentRunner.java:288)
	at org.junit.runners.ParentRunner.accessThe $000(ParentRunner.java:58)
	at org.junit.runners.ParentRunner$2.evaluate(ParentRunner.java:268)
	at org.junit.runners.ParentRunner.run(ParentRunner.java:363)
	at org.junit.runner.JUnitCore.run(JUnitCore.java:137)
	at com.intellij.junit4.JUnit4IdeaTestRunner.startRunnerWithArgs(JUnit4IdeaTestRunner.java:68)
	at com.intellij.rt.execution.junit.IdeaTestRunner$Repeater.startRunnerWithArgs(IdeaTestRunner.java:47)
	at com.intellij.rt.execution.junit.JUnitStarter.prepareStreamsAndStart(JUnitStarter.java:242)
	at com.intellij.rt.execution.junit.JUnitStarter.main(JUnitStarter.java:70)
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APIs for Creating Unmodifiable Collections

Java9 added a new of factory method whose interface parameters are individual elements, and Java10 added list. copyOf, set. copyOf, and map. copyOf to create ImmutableCollections from existing collections

  • List. The copyOf the source code
    /**
     * Returns an <a href="#unmodifiable">unmodifiable List</a> containing the elements of
     * the given Collection, in its iteration order. The given Collection must not be null,
     * and it must not contain any null elements. If the given Collection is subsequently
     * modified, the returned List will not reflect such modifications.
     *
     * @implNote
     * If the given Collection is an <a href="#unmodifiable">unmodifiable List</a>,
     * calling copyOf will generally not create a copy.
     *
     * @param <E> the {@code List}'s element type * @param coll a {@code Collection} from which elements are drawn, must be non-null * @return a {@code List} containing the elements of the given {@code Collection} * @throws NullPointerException if coll is null, or if it contains any nulls * @since 10 */ @SuppressWarnings("unchecked") static 
      
        List
       
         copyOf(Collection
         coll) { if (coll instanceof ImmutableCollections.AbstractImmutableList) { return (List
        
         )coll; } else { return (List
         
          )List.of(coll.toArray()); }}
         
        
       
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  • The instance
    @Test(expected = UnsupportedOperationException.class)
    public void testCollectionCopyOf(){
        List<String> list = IntStream.rangeClosed(1,10)
                .mapToObj(i -> "num"+i)
                .collect(Collectors.toList());
        List<String> newList = List.copyOf(list);
        newList.add("not allowed");
    }
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The toUnmodifiableList, toUnmodifiableSet, and toUnmodifiableMap methods are added

    @Test(expected = UnsupportedOperationException.class)
    public void testCollectionCopyOf(){
        List<String> list = IntStream.rangeClosed(1,10)
                .mapToObj(i -> "num"+i)
                .collect(Collectors.toUnmodifiableList());
        list.add("not allowed");
    }
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summary

The Local Variable Type Inference (307: Parallel Full GC for G1) and the 317: Parallel Full GC for G1 Experimental Java-based JIT Compiler is relatively important and worthy of further study.

doc

  • JDK 10 Features
  • Introducing Java SE 10(The official interpretation)
  • What’s New in JDK 10 – New Features and Enhancements(Official detail interpretation)
  • JDK-8140281 : (opt) add no-arg orElseThrow() as preferred alternative to get()
  • JDK-8177290 : add copy factory methods for unmodifiable List, Set, Map