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Java 9 features
- 1. Java SE 9 -SHRINATH JOSHI
- 2. Java 9 Java9 was released on 21st September 2017 The main goals for Java 9 are to: Make the Java Standard Edition platform, and the JDK, more navigable to scale down for small computing devices. Improve the overall security and maintain not only the JDK but the Java Implementations in general. Allow overall improved application performance. Make it easier for Java developers to build and uphold the code libraries and larger applications, for both the Java SE and EE Platforms.
- 3. Java 9 Features Jshell JPMS (Java Platform Module System) Jlink (Java Linker) Http/2 Client API Process API Update Private method inside interface
- 4. Java 9 Featurescont.. Try with resources enhancement Factory method to create unmodifiadble collections Stream Api enhancements < > (Diamond )operator Enhancement SafeVargs annotations G1GC (Garbage First Garbage collector)
- 5. JShell Like aplayground for Begineers where individual can start learning without writing the boilerplate code The Java Shell tool (JShell) is an interactive tool for learning the Java programming language and prototyping Java code. JShell is a Read-Evaluate-Print Loop (REPL), which evaluates declarations, statements, and expressions as they are entered and immediately shows the results. The tool is run from the command line.
- 6. JPMS Until java8 ,while developing software we first define the classes, interfaces,enum and put this inside package and then this packages is kept as Jar file. This has few disadvantages eg NoClassDefFoundError, VersionConflict, Security Problem. Untill Java 8, Jdk and Jre had monolithic structure i.e. it cannot be divided. To execute a simple hello World program of 1 kb the client had to load 400Mb of JRE on client machine. All this problem is also known as Java Hell. To overcome this problem JPMS comes into picture
- 7. In modularprogramming the Jvm checks in the start of execution where all the required files are present or no .Therefore there is no Chance of NoclasssDefFoundError. Part Of Jigsaw Project Project started in 2005
- 8. JLink To runa simple hello World program we need JRE . JRE contains rt.jar whose size is 60Mb . This rt.jar contains all the predefined class i.e it contains 4300+ classes but we required hardly 5-6 classes . The size of Jre is 400Mb . Therefore to run 1 kb program 400mb is required . Therefore java is heavy weight. To create our own customised jre we use jLink We can now use java for Iot deices,micro-services etc.
- 9. HTTP/2 Client Tosend an Http request to server from a java program we need some software and that is http/2 clinet. Until java 8 we used httpUrlConnection but this had certain drawback httpUrlconnection was developed in 1997 ,introduced in java 1.0 and was still being used until java 8. httpUrlconnection was difficult to use Only one request at a time. It supported only data in text format and not binary data. It works in blocking mode i.e wait for the next request.
- 10. Therefore Javaprogrammer started using Apache Http client or google Httpclient. Now in Java 9 they introduced Http/2 client Very easy to use Works in both blocking and non blocking mode Works with data in both text and binary format Can send multiple requests.
- 11. Process API Updates Java communication with processor is very difficult until java 8, but from java 9 new methods added to Process class i.e Api got enhanced. Most imp feature of java 9 System.out.println(ProcessHandle.current().pid()); to get the current running jvm process
- 12. Private method insideInterface Until 1.7 inside interface wecan take only public and abstract methods and every variable present inside interface is public static and final From 1.8 we can take default methods and static methods From 1.9 we can take private methods inside interface Without affecting the implementation classes we can extends the functionality of interface by adding default methods Interface inter { M1(); M2(); }
- 13. Class aimplements inter { M1() {} M2() {} } . . . Class class10 implents inter { M1(){} M2(){} }
- 14. To adda method in interface we have to make changes in all the implanting classes .therefor we add default method Interface infer { M1(){} M2(){} Default void m3(){} } Implementing classes are not required to override default methods.
- 15. Private methodsin interface are introduced to make code reuseable Without affecting implementation class how we can get Code Reusablilty?. Consider the below code Since the method is private it is hidden from the implementing class This make code reusable .
- 16. Interface interface { Defaulf void m1() { m3(); } Default void m2() { m3(); } Private void m3() { Common code; } }
- 17. Try with Resourcesenhancement Try with resources Until 1.6 , if we have to close the resources we wrote that code in finally block From 1.7 try with resources came try(r1;r2) { } These resources were closed automatically after the try block.
- 18. Fw fw=newFw(“abc.txt”); Fr fr=new Fr(“input.txt”); Try(fw;fr) { }// Not allowed in Java 8 // We have to declare inside try() From Java 9 we can use try with resources where resources are already being created
- 19. Factory Methods tocreate Unmodifiable Collections List <String> l =new ArrayList<>(); L.add(“A”); L.add(“B”); L.add(“C”); Now if I have to make list immutable?? Until Java 8 List <String > l2=Collections.unmodifiableList(l); From Java 9 List<String> l=List.of(“A”,”B”,”C”); Set.of();
- 20. Stream API Enhancement Collection is a group of objects. The main objective of collection is to hold objects as a single entitiy and Stream is used to process this object from the collections. New Methods in Java 9 takeWhile() //Default Methods in Stream Interface dropWhile() -------- ------- Stream.iterate() with three argument Stream.ofNullable() //to check if null reference
- 21. <> Operator ArrayList<String> l =new ArrayList<String>(); Generics is used to perform typesafety and perform and resolve type casting problems From Java 7 ArrayList <String> l =new ArrayList<>(); // No need to specify the type parameter Also know as type inference This <>operator is only applicable for normal classes and not applicable for Anonymous Inner Classes From Java 9 we can use <>(diamond) operator in anonymous inner classes.
- 22. safeVarargs Annotation InJava 5 m1(int … x) M1(List<String>… x) Here there may be a chance of heap Pollution. // Warning by compiler If we want to supress this warning we can go for safevarargs annotations This concept came in java 8 wherein safevarargs is used for static ,final ,constructor methods From Java 9 ,it is also used for private methods also
- 23. G1GC Garbage First Garbagecollection Many type of GC Serial Gc Parallel GC Concurrent mark and Sweep gc G1gc //from 1.6 First three will work based on generations G1gc divides the heap into parts and uses the part with most garbage i.e highest number of objects that are eligible for gc and will destroy that area Performance wise g1gc is best From Java 9 ,g1gc is default garbage collector Untill java 8 , parallel gc was default garbage collector
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