Java 8 Tutorial

Java 8 Tutorial#

Overview#

New Features#

  • Lambda expression − Adds functional processing capability to Java.

  • Method references − Referencing functions by their names instead of invoking them directly. Using functions as parameter.

  • Default method − Interface to have default method implementation.

  • New tools − New compiler tools and utilities are added like ‘jdeps’ to figure out dependencies.

  • Stream API − New stream API to facilitate pipeline processing.

  • Date Time API − Improved date time API.

  • Optional − Emphasis on best practices to handle null values properly.

  • Nashorn, JavaScript Engine − A Java-based engine to execute JavaScript code.

Lambda Expressions#

Syntax#

parameter -> expression body

Lambda Expressions Example#

MathOperation addition = (int a, int b) -> a + b;

GreetingService greetService1 = message -> System.out.println("Hello " + message);

  • LambdaSort

  • LambdaMathService

Method References#

List names = new ArrayList();
names.forEach(System.out::println);

  • MethodReferences

Functional Interfaces#

  • FunctionalInterfaces

Default Methods#

Syntax#

public interface vehicle {
   default void print() {
      System.out.println("I am a vehicle!");
   }
}

Multiple Defaults#

public interface fourWheeler {
   default void print() {
      System.out.println("I am a four wheeler!");
   }
}

public class car implements vehicle, fourWheeler {
   public void print() {
      System.out.println("I am a four wheeler car vehicle!");
   }
}

Static Default Methods#

public interface vehicle {
   default void print() {
      System.out.println("I am a vehicle!");
   }
	
   static void blowHorn() {
      System.out.println("Blowing horn!!!");
   }
}

  • DefaultMethods

Streams#

Generating Streams#

List<String> strings = Arrays.asList("abc", "", "bc", "efg", "abcd","", "jkl");
List<String> filtered = strings.stream().filter(string -> !string.isEmpty()).collect(Collectors.toList());

forEach#

Random random = new Random();
random.ints().limit(10).forEach(System.out::println);

map#

List<Integer> numbers = Arrays.asList(3, 2, 2, 3, 7, 3, 5);
//get list of unique squares
List<Integer> squaresList = numbers.stream().map( i -> i*i).distinct().collect(Collectors.toList());

filter#

List<String>strings = Arrays.asList("abc", "", "bc", "efg", "abcd","", "jkl");
//get count of empty string
int count = strings.stream().filter(string -> string.isEmpty()).count();

limit#

Random random = new Random();
random.ints().limit(10).forEach(System.out::println);

sorted#

Random random = new Random();
random.ints().limit(10).sorted().forEach(System.out::println);

Parallel Processing#

List<String> strings = Arrays.asList("abc", "", "bc", "efg", "abcd","", "jkl");
//get count of empty string
long count = strings.parallelStream().filter(string -> string.isEmpty()).count();

Collectors#

List<String>strings = Arrays.asList("abc", "", "bc", "efg", "abcd","", "jkl");
List<String> filtered = strings.stream().filter(string -> !string.isEmpty()).collect(Collectors.toList());
System.out.println("Filtered List: " + filtered);
String mergedString = strings.stream().filter(string -> !string.isEmpty()).collect(Collectors.joining(", "));
System.out.println("Merged String: " + mergedString);

Statistics#

List numbers = Arrays.asList(3, 2, 2, 3, 7, 3, 5);
IntSummaryStatistics stats = numbers.stream().mapToInt((x) -> x).summaryStatistics();
System.out.println("Highest number in List : " + stats.getMax());
System.out.println("Lowest number in List : " + stats.getMin());
System.out.println("Sum of all numbers : " + stats.getSum());
System.out.println("Average of all numbers : " + stats.getAverage());

  • Streams

Optional Class#

Class Declaration#

public final class Optional<T> extends Object

  • OptionalClass

Nashorn JavaScript#

  • NashornJavaScript

New Date/Time API#

  • LocalDateTimeAPI

  • ZonedDateTimeAPI

  • ChronoUnitsEnum

  • PeriodAndDuration

  • TemporalAdjusters

  • BackwardCompatibility

Base64#

  • Base64Example

References#

Contents