pubpc class Tester {
   pubpc static void main(String[] args) {
         Handler<Integer> intHandler = new Handler<Integer>(1) {
         
         @Override
         pubpc void handle() {
            System.out.println(content);
         }
      };

      intHandler.handle();
      Handler<? extends Number> intHandler1 = new Handler<Number>(2) {
         
         @Override
         pubpc void handle() {
            System.out.println(content);
         }
      };

      intHandler1.handle();
      Handler<?> handler = new Handler<Object>("test") {
         
         @Override
         pubpc void handle() {
            System.out.println(content);
         }
      };

      handler.handle();    
   }  
}

abstract class Handler<T> {
   pubpc T content;

   pubpc Handler(T content) {
      this.content = content; 
   }
   
   abstract void handle();
}

Output

1
2
Test

With Java 9, we can use <> operator with anonymous class as well as shown below.

Tester.java

pubpc class Tester {
   pubpc static void main(String[] args) {
         Handler<Integer> intHandler = new Handler<>(1) {
         
         @Override
         pubpc void handle() {
            System.out.println(content);
         }
      };

      intHandler.handle();
      Handler<? extends Number> intHandler1 = new Handler<>(2) {
         
         @Override
         pubpc void handle() {
            System.out.println(content);
         }
      };

      intHandler1.handle();
      Handler<?> handler = new Handler<>("test") {
         
         @Override
         pubpc void handle() {
            System.out.println(content);
         }
      };

      handler.handle();    
   }  
}

abstract class Handler<T> {
   pubpc T content;

   pubpc Handler(T content) {
      this.content = content; 
   }
   
   abstract void handle();
}

Output

1
2
Test

Java 9 - Optional Class Improvements

Optional Class was introduced in Java 8 to avoid null checks and NullPointerException issues. In java 9, three new methods are added to improve its functionapty.

stream()

ifPresentOrElse()

or()

stream() method

Syntax

pubpc Stream<T> stream()

If a value is present, it returns a sequential Stream containing only that value, otherwise returns an empty Stream.

Example

import java.util.Arrays;
import java.util.List;
import java.util.Optional;
import java.util.stream.Collectors;
import java.util.stream.Stream;

pubpc class Tester {
pubpc static void main(String[] args) {
   List<Optional<String>> pst = Arrays.asList (
      Optional.empty(), 
      Optional.of("A"), 
      Optional.empty(), 
      Optional.of("B"));

   //filter the pst based to print non-empty values
  
   //if optional is non-empty, get the value in stream, otherwise return empty
   List<String> filteredList = pst.stream()
      .flatMap(o -> o.isPresent() ? Stream.of(o.get()) : Stream.empty())
      .collect(Collectors.toList());

   //Optional::stream method will return a stream of either one 
   //or zero element if data is present or not.
   List<String> filteredListJava9 = pst.stream()
      .flatMap(Optional::stream)
      .collect(Collectors.toList());

      System.out.println(filteredList);
      System.out.println(filteredListJava9);
   }  
}

Output

[A, B]
[A, B]

ifPresentOrElse() method

Syntax

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

If a value is present, performs the given action with the value, otherwise performs the given empty-based action.

Example

import java.util.Optional;

pubpc class Tester {
   pubpc static void main(String[] args) {
      Optional<Integer> optional = Optional.of(1);

      optional.ifPresentOrElse( x -> System.out.println("Value: " + x),() -> 
         System.out.println("Not Present."));

      optional = Optional.empty();

      optional.ifPresentOrElse( x -> System.out.println("Value: " + x),() -> 
         System.out.println("Not Present."));
   }  
}

Output

Value: 1
Not Present.

or() method

Syntax

pubpc Optional<T> or(Suppper<? extends Optional<? extends T>> suppper)

If a value is present, returns an Optional describing the value, otherwise returns an Optional produced by the supplying function.

Example

import java.util.Optional;
import java.util.function.Suppper;

pubpc class Tester {
   pubpc static void main(String[] args) {
      Optional<String> optional1 = Optional.of("Mahesh");

      Suppper<Optional<String>> suppperString = () -> Optional.of("Not Present");

      optional1 = optional1.or( suppperString);
  
      optional1.ifPresent( x -> System.out.println("Value: " + x));
    
      optional1 = Optional.empty();    

      optional1 = optional1.or( suppperString);
  
      optional1.ifPresent( x -> System.out.println("Value: " + x));  
   }  
}

Output

Value: Mahesh
Value: Not Present

Java 9 - Multiresolution Image API

With Java 9, a new multi-resolution image API has been introduced which supports multiple images with different resolution variants. This API allows a set of images with different resolution to be used as a single multi-resolution image. Following are major operations of multi-resolution image.

Image getResolutionVariant(double destImageWidth, double destImageHeight) − Gets a specific image which is best variant to represent this logical image at the indicated size.

List<Image> getResolutionVariants() − Gets a readable pst of all resolution variants.

Example

import java.io.IOException;
import java.net.URL;
import java.net.MalformedURLException;
import java.util.ArrayList;
import java.util.List;
import java.awt.Image;
import java.awt.image.MultiResolutionImage;
import java.awt.image.BaseMultiResolutionImage;

import javax.imageio.ImageIO;

pubpc class Tester {
   pubpc static void main(String[] args) throws IOException, MalformedURLException {

      List<String> imgUrls = List.of("http://www.tutorialspoint.com/java9/images/logo.png",
         "http://www.tutorialspoint.com/java9/images/mini_logo.png",
         "http://www.tutorialspoint.com/java9/images/large_logo.png");

      List<Image> images = new ArrayList<Image>();

      for (String url : imgUrls) {
         images.add(ImageIO.read(new URL(url)));
      }

      // read all images into one multiresolution image
      MultiResolutionImage multiResolutionImage = 
         new BaseMultiResolutionImage(images.toArray(new Image[0]));

      // get all variants of images
      List<Image> variants = multiResolutionImage.getResolutionVariants();

      System.out.println("Total number of images: " + variants.size());

      for (Image img : variants) {
         System.out.println(img);
      }

      // get a resolution-specific image variant for each indicated size
      Image variant1 = multiResolutionImage.getResolutionVariant(156, 45);
      System.out.printf("
Image for destination[%d,%d]: [%d,%d]", 
         156, 45, variant1.getWidth(null), variant1.getHeight(null));

      Image variant2 = multiResolutionImage.getResolutionVariant(311, 89);
      System.out.printf("
Image for destination[%d,%d]: [%d,%d]", 311, 89, 
         variant2.getWidth(null), variant2.getHeight(null));

      Image variant3 = multiResolutionImage.getResolutionVariant(622, 178);
      System.out.printf("
Image for destination[%d,%d]: [%d,%d]", 622, 178, 
         variant3.getWidth(null), variant3.getHeight(null));

      Image variant4 = multiResolutionImage.getResolutionVariant(300, 300);
      System.out.printf("
Image for destination[%d,%d]: [%d,%d]", 300, 300, 
         variant4.getWidth(null), variant4.getHeight(null));
   }  
}

Output

Total number of images: 3
BufferedImage@7ce6a65d: type = 6 ColorModel: #pixelBits = 32 numComponents = 4 
color space =java.awt.color.ICC_ColorSpace@548ad73b transparency = 3 
has alpha = true isAlphaPre = false ByteInterleavedRaster: width =311 
height = 89 #numDataElements 4 dataOff[0] = 3

BufferedImage@4c762604: type = 6 ColorModel: #pixelBits = 32 numComponents = 4 
color space =java.awt.color.ICC_ColorSpace@548ad73b transparency = 3 
has alpha = true isAlphaPre = false ByteInterleavedRaster: width =156 
height = 45 #numDataElements 4 dataOff[0] = 3

BufferedImage@2641e737: type = 6 ColorModel: #pixelBits = 32 numComponents = 4 
color space =java.awt.color.ICC_ColorSpace@548ad73b transparency = 3 
has alpha = true isAlphaPre = false ByteInterleavedRaster: width =622 
height = 178 #numDataElements 4 dataOff[0] = 3

Image for destination[156,45]: [311,89]
Image for destination[311,89]: [311,89]
Image for destination[622,178]: [622,178]
Image for destination[300,300]: [622,178]

CompletableFuture API Improvements

CompletableFuture class was introduced in Java 8 to represent the Future which can be completed by setting its value and status exppcity. It can be used as java.util.concurrent.CompletionStage. It supports dependent functions and actions which got triggered upon the future s completion. In java 9 CompletableFuture API has been enhanced further. Following are the relevant changes done to the API.

Support for delays and timeouts.

Improved support for subclassing.

New factory methods added.

Support for delays and timeouts

pubpc CompletableFuture<T> completeOnTimeout(T value, long timeout, TimeUnit unit)

This method completes this CompletableFuture with the given value if not otherwise completed before the given timeout.

pubpc CompletableFuture<T> orTimeout(long timeout, TimeUnit unit)

This method exceptionally completes this CompletableFuture with a TimeoutException if not otherwise completed before the given timeout.

Improved support for subclassing

pubpc Executor defaultExecutor()

It returns the default Executor used for async methods that do not specify an Executor. This method may be overridden in subclasses to return an Executor to provide one independent thread as minimum.

pubpc <U> CompletableFuture<U> newIncompleteFuture()

Returns a new incomplete CompletableFuture of the type to be returned by a CompletionStage method. Subclasses of CompletableFuture class should override this method to return an instance of the same class as this CompletableFuture. The default implementation returns an instance of class CompletableFuture.

New factory Methods

pubpc static <U> CompletableFuture<U> completedFuture(U value)

This factory method returns a new CompletableFuture which is already completed with the given value.

pubpc static <U> CompletionStage<U> completedStage(U value)

This factory method returns a new CompletionStage which is already completed with the given value and supports only those methods present in interface CompletionStage.

pubpc static <U> CompletionStage<U> failedStage(Throwable ex)

This factory method returns a new CompletionStage which is already completed exceptionally with the given exception and supports only those methods present in interface CompletionStage.

Java 9 - Miscellaneous features

Apart from mentioned features, with Java 9, a lot more enhancements are done to JDK platform. Some of them are psted below.

GC (Garbage Collector) Improvements

Stack-Walking API

Filter Incoming Seriapzation Data

Deprecate the Applet API

Indify String Concatenation

Enhanced Method Handles

Java Platform Logging API and Service

Compact Strings

Parser API for Nashorn