Java 8 Features

Functional Interface

• An Interface that has only one abstract method. 
• There can be default interface methods.
• There can be static methods.
• Current Examples are Runnable / Callable / Comparator

    public class FunctionalInterfaceEx {
        @FunctionalInterface        

        public interface Functional {
           void method();
        }

Lambda Expressions

• Can replace any Functional Interface

    Arrays.asList("a", "b", "d").forEach

    ( e -> {

            System.out.print( e );
            System.out.print( e );
        } 

    ); 

Interface : Default Methods

• New methods added to existing Interfaces.
• Implementors need not override these. 
• Evolves the interface. Current examples : 
• java.util.Collection  [ stream(), parallelStream(), removeIf()]
• java.util.Iterable [ forEach() ]
• java.util.List [ replaceAll() ] 

    private interface DefaultMethods {
        default String notRequired() {
            return "Default implementation";
        }
    }

Interface - Static Methods



     
    public class StaticMethods {
        static List create(Supplier<List> supplier) {
            return supplier.get();
        }
    }

Method Reference 

Class :: new 
Class :: static_methods 
Class :: method 
instance :: method

Repeating Annotations

@Filter( "filter1" ) 
@Filter( "filter2" ) 
public interface Filterable { 


}

Better Type Inference

     final Value< String > value = new Value<>();

Extended Annotations Support

• Now, it is possible to annotate mostly everything: local variables, generic types, super-classes and implementing interfaces, even the method’s exceptions declaration

Parameter Names

• Preserve Parameters names in bytecode.
• Compile with -parameters argument [ javac Abc -parameters]

Optional - In line Guava library.

• isPresent(), get(), empty(), ofNullable(T t) 

Streams - java.util.stream - Functional style programming. Collections Processing

• Collection.stream().filter()
• Collection.stream().parallel().map(fn).reduce(fn)
• Collection.stream().mapToDouble(fn).mapToInt(fn)
• Collection.stream().serial().collect()

New Date Time Library - 

• JSR 310
• Influenced by Joda-Time, Immutable 
• java.time.Clock 
• java.time.LocalDate 
• java.time.LocalTime
• java.time.LocalDateTime
• java.time.ZonedDateTime
• java.time.Duration
• java.time.Instant

Nashorn JavaScript engine

Parallel Arrays

• parallelSetAll()
• parallelSort() 

Concurrency

• New methods added to ConcurrentHashMap & ForkJoinPool
• New class - java.util.concurrent.locks.StampedLock

Class Dependency Analyser

JVM Features - Permgen is gone

• JEP 122
• Replaced with Metaspace - Used native memory for the representation of class metadata