Java10- New features you should be aware of
10 Java 10 Features Developer Should Know
Java SE 10 was created in close collaboration with the OpenJDK Community, a diverse set of contributors whom have collaborated for more than ten years on an open-source implementation of the Java SE platform. Key features in the new release include:
Here is a quick note on those features:
1. Local Variable Type Inference (JEP 286)
Similar to Javascript, Kotlin, and Scala, now Java will also have a var keyword which allows you to declare a local variable without specifying its type. The type will be inferred from context for example when you say var name = "Java" then compile will already know the type is String.
I don't know how useful this will be as I am quite used to of seeing int i =0 or String name = "Java" and I liked the type information present in the variable declaration line but looks like Java is going the way Scala and Kotlin are and trying to incorporate changes from there.
Also, note that the var keyword can only be used for local variables i.e. variables inside methods or code blocks, you cannot use it for member variable declaration inside the class body.
And, finally, it doesn't make Java a dynamically typed language like Python, Java is still a statically typed language and once the type is assigned you cannot change it. For example, var name = "Java" is ok but then name = 3; is not ok.
As Sander Mak puts in his Pluarlsight course What's New in Java 10 this is one of the most eye-catching features of Java 10 which reduces the amount of boilerplate code needed to declare local variables in Java.
It's not so obvious from simple example but considers where a method returns a complex list type which requires a lot of angle brackets and generics to declare the type, this really saves time in those case:
var list = List.of(1, 2.0, "3")
Here list will be inferred as List<? extends Serializable & Comparable<..>> which is an intersection type.
2. Time-Based Release Versioning (JEP 322)
From JDK 10 release, Java has adopted a new schedule of a new release every six months. There is a lot of debate whether this is a practical approach or not as many are saying that its good that you will get new features every six month and many are complaining that its too little a time to adopt a JDK.
Anyway, this will be the way forward with an LTS release every three years, consider that a major release.
Also, The Update element will increment one month after the Feature element is incremented so the April 2018 Java release will be JDK 10.0.1, July 2018 release will be named JDK 10.0.2 and so on.
3. Garbage-Collector Interface (JEP 304)
This is one more interesting and useful Java 10 features which increases code isolation of different garbage collectors and introduces a clean interface for garbage collectors.
This means it easier to exclude a GC from a JDK build and it also easier to add a new GC without it affecting the code base. You can further see Java Memory Management to learn more about G1 Garbage Collection and difference between G1 and Concurrent Mark Sweep Garbage collector.
4. Parallel Full GC for G1 (JEP 307)
Another interesting feature which improves G1 worst-case latencies by making the full GC parallel.
If you remember, In Java 9 release, G1 was made the default GC for JVM, which was designed to avoid full GC, but when the concurrent collections couldn’t reclaim memory quick enough it would end up falling back on a full GC, and that creates a problem.
This change will parallelize the full GC algorithm so that in the unlikely event of a G1 Full GC, same number of threads can be used as in the concurrent collections to improve the overall performance.
If you want to learn more about Parallel Full GC for G1 then you should watch What's New in Java 10 by Sander Mak to learn about the performance improvement done on Java 10 release. He has nicely put together some important JDK feature in a short course on Pluarlsight.
5. Heap Allocation on Alternative Memory Devices (JEP 316)
This sounds a really cool feature which enables the HotSpot VM to allocate the Java object heap on an alternative memory device, specified by the user.
For example, this feature makes it possible to assign lower priority processes to use the NV-DIMM memory, and instead only allocate the higher priority processes to the DRAM in a multi-JVM environment.
Btw, If you don't know much about JVM, I suggest you to first start with Understanding the Java Virtual Machine: Memory Management By Kevin Jones, a good introductory course on JVM.
6. Consolidate the JDK Forest into a Single Repository (JEP 296)
This new Java 10 feature is all about housekeeping. It will combine the numerous repositories of the JDK forest into a single repository.
7. Root Certificates (JEP 319)
This is another important change Java 10 is bringing. If you remember, JDK 10 was created with the close collaboration with OpenJDK and this is evident from this feature.
It will provide a default set of root Certification Authority making OpenJDK builds more appealing to developers.
It also aims to reduce the difference between the OpenJDK and Oracle JDK builds. Critical security components such as TLS will now work by default in OpenJDK builds
8. Experimental Java-Based JIT Compiler (JEP 317)
This is another interesting feature which enables the Java-based JIT compiler, Graal, to be used as an experimental JIT compiler on the Linux/x64 platform.
If you remember, Graal was already added back in Java 9, but now you can enable it with the following JVM arguments:
-XX:+UnlockExperimentalVMOptions -XX:+UseJVMCICompiler
If you don't know Grall is a new Java-based JIT compiler which is the basis of an experimental Ahead-of-Time (AOT) compiler.
However, keep in mind that it is in an experimental stage and you should not use it for production.
9. Thread-Local Handshakes (JEP 312)
This Java 10 feature lays the groundwork for improved VM performance, by making it possible to execute a callback on application threads without performing a global VM savepoint. This would mean that the JVM could stop individual threads and not just all of them.
There are several small improvements done as part of this feature or JEP 312 to improve VM performance e.g. some memory barriers have been removed the JVM and biased locking is improved by only stopping individual threads for revoking biases.
10. Remove the Native-Header Generation Tool (JEP 313)
This is another Java 10 feature which focuses on housekeeping. It will remove the javah tool from the JDK, a separate tool to generate header files when compiling JNI code, as this can be done through javac.
That's all about some interesting features of Java 10 or JDK 10. There are a lot more low level and API changes which you can find on Oracle's official release notes. I'll also blog about those changes as and when I come to know about, so you can stay tuned for more JDK 10 articles and tutorials here in Javarevisited.
You can download JDK 10 from Oracle's website to play with the new features.
Java SE 10 was created in close collaboration with the OpenJDK Community, a diverse set of contributors whom have collaborated for more than ten years on an open-source implementation of the Java SE platform. Key features in the new release include:
- Local-variable type inference: enhances the Java language to extend type inference to declarations of local variables with initializers.
- Parallel Full GC for G1: improves G1 worst-case latencies by making the full GC parallel.
- Application Class-Data Sharing: optimizes startup time and footprint by extending the existing Class-Data Sharing ("CDS") feature to allow application classes to be placed in the shared archive.
- Experimental Java-Based JIT Compiler: enables the Java-based JIT compiler, Graal, to be used as an experimental JIT compiler on the Linux/x64 platform
Here is a quick note on those features:
1. Local Variable Type Inference (JEP 286)
Similar to Javascript, Kotlin, and Scala, now Java will also have a var keyword which allows you to declare a local variable without specifying its type. The type will be inferred from context for example when you say var name = "Java" then compile will already know the type is String.
I don't know how useful this will be as I am quite used to of seeing int i =0 or String name = "Java" and I liked the type information present in the variable declaration line but looks like Java is going the way Scala and Kotlin are and trying to incorporate changes from there.
Also, note that the var keyword can only be used for local variables i.e. variables inside methods or code blocks, you cannot use it for member variable declaration inside the class body.
And, finally, it doesn't make Java a dynamically typed language like Python, Java is still a statically typed language and once the type is assigned you cannot change it. For example, var name = "Java" is ok but then name = 3; is not ok.
As Sander Mak puts in his Pluarlsight course What's New in Java 10 this is one of the most eye-catching features of Java 10 which reduces the amount of boilerplate code needed to declare local variables in Java.
It's not so obvious from simple example but considers where a method returns a complex list type which requires a lot of angle brackets and generics to declare the type, this really saves time in those case:
var list = List.of(1, 2.0, "3")
Here list will be inferred as List<? extends Serializable & Comparable<..>> which is an intersection type.
2. Time-Based Release Versioning (JEP 322)
From JDK 10 release, Java has adopted a new schedule of a new release every six months. There is a lot of debate whether this is a practical approach or not as many are saying that its good that you will get new features every six month and many are complaining that its too little a time to adopt a JDK.
Anyway, this will be the way forward with an LTS release every three years, consider that a major release.
Also, The Update element will increment one month after the Feature element is incremented so the April 2018 Java release will be JDK 10.0.1, July 2018 release will be named JDK 10.0.2 and so on.
3. Garbage-Collector Interface (JEP 304)
This is one more interesting and useful Java 10 features which increases code isolation of different garbage collectors and introduces a clean interface for garbage collectors.
This means it easier to exclude a GC from a JDK build and it also easier to add a new GC without it affecting the code base. You can further see Java Memory Management to learn more about G1 Garbage Collection and difference between G1 and Concurrent Mark Sweep Garbage collector.
4. Parallel Full GC for G1 (JEP 307)
Another interesting feature which improves G1 worst-case latencies by making the full GC parallel.
If you remember, In Java 9 release, G1 was made the default GC for JVM, which was designed to avoid full GC, but when the concurrent collections couldn’t reclaim memory quick enough it would end up falling back on a full GC, and that creates a problem.
This change will parallelize the full GC algorithm so that in the unlikely event of a G1 Full GC, same number of threads can be used as in the concurrent collections to improve the overall performance.
If you want to learn more about Parallel Full GC for G1 then you should watch What's New in Java 10 by Sander Mak to learn about the performance improvement done on Java 10 release. He has nicely put together some important JDK feature in a short course on Pluarlsight.
5. Heap Allocation on Alternative Memory Devices (JEP 316)
This sounds a really cool feature which enables the HotSpot VM to allocate the Java object heap on an alternative memory device, specified by the user.
For example, this feature makes it possible to assign lower priority processes to use the NV-DIMM memory, and instead only allocate the higher priority processes to the DRAM in a multi-JVM environment.
Btw, If you don't know much about JVM, I suggest you to first start with Understanding the Java Virtual Machine: Memory Management By Kevin Jones, a good introductory course on JVM.
6. Consolidate the JDK Forest into a Single Repository (JEP 296)
This new Java 10 feature is all about housekeeping. It will combine the numerous repositories of the JDK forest into a single repository.
7. Root Certificates (JEP 319)
This is another important change Java 10 is bringing. If you remember, JDK 10 was created with the close collaboration with OpenJDK and this is evident from this feature.
It will provide a default set of root Certification Authority making OpenJDK builds more appealing to developers.
It also aims to reduce the difference between the OpenJDK and Oracle JDK builds. Critical security components such as TLS will now work by default in OpenJDK builds
8. Experimental Java-Based JIT Compiler (JEP 317)
This is another interesting feature which enables the Java-based JIT compiler, Graal, to be used as an experimental JIT compiler on the Linux/x64 platform.
If you remember, Graal was already added back in Java 9, but now you can enable it with the following JVM arguments:
-XX:+UnlockExperimentalVMOptions -XX:+UseJVMCICompiler
If you don't know Grall is a new Java-based JIT compiler which is the basis of an experimental Ahead-of-Time (AOT) compiler.
However, keep in mind that it is in an experimental stage and you should not use it for production.
9. Thread-Local Handshakes (JEP 312)
This Java 10 feature lays the groundwork for improved VM performance, by making it possible to execute a callback on application threads without performing a global VM savepoint. This would mean that the JVM could stop individual threads and not just all of them.
There are several small improvements done as part of this feature or JEP 312 to improve VM performance e.g. some memory barriers have been removed the JVM and biased locking is improved by only stopping individual threads for revoking biases.
10. Remove the Native-Header Generation Tool (JEP 313)
This is another Java 10 feature which focuses on housekeeping. It will remove the javah tool from the JDK, a separate tool to generate header files when compiling JNI code, as this can be done through javac.
That's all about some interesting features of Java 10 or JDK 10. There are a lot more low level and API changes which you can find on Oracle's official release notes. I'll also blog about those changes as and when I come to know about, so you can stay tuned for more JDK 10 articles and tutorials here in Javarevisited.
You can download JDK 10 from Oracle's website to play with the new features.
Nice Inormation
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