Java 8 New Feature

Java 8 new Feature

· forEach() method in Iterable interface.

· forEachOrdered() method for Java Stream

· Java Time API.

· default and static methods in Interfaces.

· Collection API improvements.

· Concurrency API improvements.

· Functional Interfaces and Lambda Expressions.

· Java Stream API for Bulk Data Operations on Collections.

· Java IO improvements.

· optional class

· final class StringJoiner

· java optional classes and optional methods

1> forEach() -

In Java 8 a new method forEach() is added to iterate the elements. It is defined in Iterable and Stream interfaces. It is a default method defined in the Iterable interface. Collection classes which extends Iterable interface can use forEach() method to iterate elements. You can use lambda expression as an argument.Because this method can take single parameter which is a functional interface..

forEach() method signature in Iterable Interface

default void forEach(Consumer<super C>action)

Example1 :-forEach() using Lamda Expression

1. import java.util.ArrayList;

2. import java.util.List;

3. public class ForEachExample001 {

4 public static void main(String[] args) {

5 List<String> toysList = new ArrayList<String>();

6 toysList.add("Football");

7 toysList.add("Ball");

8 toysList.add("Doll");

9 toysList.add("Car");

1 System.out.println("*******Iterating by passing lambda expression********");

1 toysList.forEach(toys -> System.out.println(toys));

1 }

output :

*******Iterating by passing lambda expression********

Football

Ball

Doll

Car

Example2 :-forEach() using functional interface

import java.util.ArrayList;

import java.util.Iterator;

import java.util.List;

import java.util.function.Consumer;

import java.lang.Integer;

public class ForEachExample002 {

public static void main(String[] args) {

//creating sample Collection

List<Integer> list0 = new ArrayList<Integer>();

for(int a=0; a<10; a++) list0.add(a);

//traversing using Iterator

Iterator<Integer> it = list0.iterator();

while(it.hasNext()){

Integer n = it.next();

System.out.println("Iterator Value::"+n);

}

//traversing through forEach method of Iterable with anonymous class

list0.forEach(new Consumer<Integer>() {

public void accept(Integer t) {

System.out.println("forEach anonymous class Value::"+t);

}

});

//traversing with Consumer interface implementation

MyConsumer action = new MyConsumer();

list0.forEach(action);

}

//Consumer implementation that can be reused

class MyConsumer implements Consumer<Integer>{

public void accept(Integer t) {

System.out.println("Consumer Impl Value::"+t);

}

output :

Iterator Value::0

Iterator Value::1

Iterator Value::2

Iterator Value::3

Iterator Value::4

Iterator Value::5

Iterator Value::6

Iterator Value::7

Iterator Value::8

Iterator Value::9

forEach anonymous class Value::0

forEach anonymous class Value::1

forEach anonymous class Value::2

forEach anonymous class Value::3

forEach anonymous class Value::4

forEach anonymous class Value::5

forEach anonymous class Value::6

forEach anonymous class Value::7

forEach anonymous class Value::8

forEach anonymous class Value::9

Consumer Impl Value : 0

Consumer Impl Value : 1

Consumer Impl Value : 2

Consumer Impl Value : 3

Consumer Impl Value : 4

Consumer Impl Value : 5

Consumer Impl Value : 6

Consumer Impl Value : 7

Consumer Impl Value : 8

Consumer Impl Value : 9

Example3 :-forEach() by passing method reference

import java.util.ArrayList;

import java.util.List;

public class ForEachExample001 {

public static void main(String[] args) {

List<String> toysList = new ArrayList<String>();

toysList.add("Football");

toysList.add("Ball");

toysList.add("Doll");

toysList.add("Car");

System.out.println("*******Iterating by passing method reference********");

toysList.forEach(System.out::println);

}

output :

*******Iterating by passing method reference********

Football

Ball

Doll

Car

2> forEachOrdered() - method for Java Stream iterator

It is used to iterate elements in the order specified by the stream.

forEachOrdered() method signature:-

void forEachOrdered(Consumer<super C>action)

Example :-forEachOrdered()

import java.util.ArrayList;

import java.util.List;

public class ForEachOrderedExample00 {

public static void main(String[] args) {

List<String> toyslist = new ArrayList<String>();

toyslist.add("Football");

toyslist.add("Car");

toyslist.add("Bus");

toyslist.add("Doll");

System.out.println("*****Iterating by passing lambda expression******");

toyslist.stream().forEachOrdered(toys -> System.out.println(toys));

System.out.println("******Iterating by passing method reference*****");

toyslist.stream().forEachOrdered(System.out::println);

}

output :

*****Iterating by passing lambda expression******

Football

Car

Bus

Doll

******Iterating by passing method reference*****

Football

Car

Bus

Doll

3> default and static method in Interface :-

Before Java 8 there no method body in interface, but know from java 8 there is a two different type of methods with body are static and default methods, to declare default and static method with there body inside interface.

forEach():-signature is-

default void forEach(Consumer<super C>action){

Objects.requireNonNull(action);

for(C c:this){

action.accept(c);

}

which is declare inside iterable interface.

The concept of default method is used to define a method with default implementation. You can override default method also to provide more specific implementation for the method.

Static method is used to defined utility methods.

Multiple Inheritance is not possible in java classes because it lead to big problems. But it handled in interface.

know interfaces are similar to abstract classes.But for this concept we must provide implementation logic in implementing class otherwise compiler will throw exception.

Example1 :-default method inside interface

interface S1{

// Default method

default void s1(){

System.out.println("Hello, it is default method");

}

// Abstract method

void s2(String msg);

}

public class DefaultMethods implements S1{

//implementing abstract method

public void s2(String msg){

System.out.println(msg);

}

public static void main(String[] args) {

DefaultMethods dem = new DefaultMethods();

//calling default method

dem.s1();

//calling abstract method

dem.s2("Java 8 Having New Features");

}

output :

Hello, it is default method

Java 8 Having New Features

Example2 :-static method inside interface

interface I2{

// default method

default void m1(){

System.out.println("Hello, it is default method");

}

// Abstract method

void m2(String str);

// static method

static void m3(String str){

System.out.println(str);

}

public class DefaultMethods00 implements I2{

// implementing abstract method

public void m2(String str){

System.out.println(str);

}

public static void main(String[] args) {

DefaultMethods00 dem0 = new DefaultMethods00();

// calling default method

dem0.m1();

// calling abstract method

dem0.m2("Java 8 having New Features");

// calling static method

I2.m3("See Carefully....");

}

output :

Hello, it is default method

Java 8 having New Features

See Carefully....

Example3 :-static and default both methods inside interface

Interface01:-

package com.DefaultAndStaticMethods;

@FunctionalInterface

public interface Interface01 {

void m1(String str);

default void logging(String str){

System.out.println("I1 logging::"+str);

}

static void printing(String str){

System.out.println("Printing "+str);

}

//trying to override Object method gives compile time error as

//"A default method cannot override a method from java.lang.Object"

// default String toString(){

// return "i1";

// }

}

Interface02 :-

package com.DefaultAndStaticMethods;

@FunctionalInterface

public interface Interface02 {

void m2();

default void logging(String str){

System.out.println("I2 logging::"+str);

}

MyClassTest :-

package com.DefaultAndStaticMethods;

public class MyClassTest implements Interface01, Interface02 {

@Override

public void m2() {

}

@Override

public void m1(String str) {

}

//MyClassTest won't compile without having it's own logging() implementation

@Override

public void logging(String str){

System.out.println("MyClassTest logging::"+str);

Interface01.printing("abc");

}

Important points about java interface static method:

1. Java interface static method is part of interface, we can’t use it for implementation class objects.

2. Java interface static methods are good for providing utility methods, for example null check, collection sorting etc.

3. Java interface static method helps us in providing security by not allowing implementation classes to override them.

4. We can’t define interface static method for Object class methods, we will get compiler error as “This static method cannot hide the instance method from Object”. This is because it’s not allowed in java, since Object is the base class for all the classes and we can’t have one class level static method and another instance method with same signature.

5. We can use java interface static methods to remove utility classes such as Collections and move all of it’s static methods to the corresponding interface, that would be easy to find and use.

> Abstract Class vs Interface in java 8

Due to addition of two methods default and static methods inside the interface.Know we can say An interface and an abstract class is almost similar except that you can create constructor in the abstract class whereas you can't do this in interface.

Example :-

abstract class AbstractClass{

// constructor

public AbstractClass() {

System.out.println("You can create constructor in abstract class");

}

// abstract method

abstract int add(int a, int b);

// non-abstract method

int sub(int a, int b){

return a-b;

}

// static method

static int multiply(int a, int b){

return a*b;

}

public class AbstractTest extends AbstractClass{

// implementing abstract method

public int add(int a, int b){

return a+b;

}

public static void main(String[] args) {

AbstractTest a = new AbstractTest();

// calling abstract method

int result1 = a.add(20, 18);

// calling non-abstract method

int result2 = a.sub(20, 18);

// calling static method

int result3 = AbstractClass.multiply(20, 18);

System.out.println("Addition: "+result1);

System.out.println("Substraction: "+result2);

System.out.println("Multiplication: "+result3);

}

output :

You can create constructor in abstract class

Addition: 38

Substraction: 2

Multiplication: 360

4> final class StringJoiner

In Java 8 new final class StringJoiner added in java.util package. It is used to construct a sequence of characters separated by a delimiter. Now, you can create string by passing delimiters like comma(,), hyphen(-) etc. You can also pass prefix and suffix to the char sequence.

There is a big difference between StingBuilder And StringJoiner. StringBuilder provides append() method but StringJoiner provides join().

The append() method doesn't know that you don't need to add delimiter after the last element but join() does. So you don't need to handle either first or last element in joining loop anymore.

And StringJoiner is used for Java Stream.

Example1 :-joining of java stream by comma
StringJoiner joiner=new StringJoiner(",");
joiner.join("Sony");
String joined=joiner.toString();
Public StringJoiner(CharSequence delimiter)
Public StringJoiner(CharSequence delimiter,CharSequence prefix,CharSequence suffix)
Public StringJoiner add(CharSequence newElement)

joiner.join("Samsung");

joiner.join("Nokia");

joiner.join("Lenovo");

StringJoiner Constructor :-

StringJoiner methods :-

Public StringJoiner merge(CharSequence newElement)

Public int length();

Public StringJoiner setEmptyValue(charSequence emptyValue)

Example2 :-joining of java stream by comma

import java.util.StringJoiner;

public class StringJoinerExample {

public static void main(String[] args) {

// passing comma(,) as delimiter

StringJoiner joinNames = new StringJoiner(",");

// Adding values to StringJoiner

joinNames.add("Rahul");

joinNames.add("Raju");

joinNames.add("Peter");

joinNames.add("Raheem");

System.out.println(joinNames);

}

output :

Rahul,Raju,Peter,Raheem

Example3 :-adding prefix and suffix

import java.util.StringJoiner;

public class StringJoinerExample {

public static void main(String[] args) {

// passing comma(,) and square-brackets as delimiter

StringJoiner joinNames = new StringJoiner(",", "[", "]");

// Adding values to StringJoiner

joinNames.add("Rahul");

joinNames.add("Raju");

joinNames.add("Peter");

joinNames.add("Raheem");

System.out.println(joinNames);

}

output :

Rahul,Raju,Peter,Raheem

Example3 :-Merge two StringJoiner

import java.util.StringJoiner;

public class StringJoinerExample {

public static void main(String[] args) {

// passing comma(,) and square-brackets as delimiter

StringJoiner joinNames = new StringJoiner(",", "[", "]");

// Adding values to StringJoiner

joinNames.add("Rahul");

joinNames.add("Raju");

// Creating StringJoiner with :(colon) delimiter

// passing colon(:) and square-brackets as delimiter

StringJoiner joinNames2 = new StringJoiner(":", "[", "]");

// Adding values to StringJoiner

joinNames2.add("Peter");

joinNames2.add("Raheem");

// Merging two StringJoiner

StringJoiner merge = joinNames.merge(joinNames2);

System.out.println(merge);

}

output :

[Rahul,Raju,Peter:Raheem]

Example3 :-StringJoiner methods

import java.util.StringJoiner;

public class StringJoinerExample {

public static void main(String[] args) {

// passing comma(,) as delimiter

StringJoiner joinNames = new StringJoiner(",");

// Prints nothing because it is empty

System.out.println(joinNames);

// We can set default empty value.

joinNames.setEmptyValue("It is empty");

System.out.println(joinNames);

// Adding values to StringJoiner

joinNames.add("Rahul");

joinNames.add("Raju");

System.out.println(joinNames);

// Returns length of StringJoiner

int length = joinNames.length();

System.out.println("Length: "+length);

// Returns StringJoiner as String type

String str = joinNames.toString();

System.out.println(str);

// Now, we can apply String methods on it

char ch = str.charAt(3);

System.out.println("Character at index 3: "+ch);

// Adding one more element

joinNames.add("Sorabh");

System.out.println(joinNames);

// Returns length

int newLength = joinNames.length();

System.out.println("New Length: "+newLength);

}

output :

It is empty

Rahul,Raju

Length: 10

Rahul,Raju

Character at index 3: u

Rahul,Raju,Sorabh

New Length: 17

5> Optional class :-

In Java 8 there is new class introduces know as optional class.It is a public final class used to deal with NullPointerException in java applications.But for using this class need to import java.util package. It provides method to check the presence of values of particular variables.

Optional is a container of object which is used to contains "not-null object".Optional object is used to present null with absent value. This class has various utility methods to facilitate code to handle values as 'available' or 'not available' instead of checking null values.

Optional class Methods :-

public static <T> Optional<T> empty()

public static <T> Optional<T> of(T value)

public static <T> Optional<T> ofNullable(T value)

public T get()

public boolean isPresent()

public void ifPresent(Consumer<? super T> consumer)

public Optional<T> filter(Predicate<? super T> predicate)

public Optional map(Function<? super T,? extends U> mapper)

public Optional flatMap(Function<? super T,Optional mapper)

public T orElse(T other)

public T orElseGet(Supplier<? extends T> other)

public <X extends Throwable> T orElseThrow(Supplier<? extends X> exceptionSupplier) throws X extends Throwable

public boolean equals(Object obj)

public int hashCode()

public String toString()

Example1 :-Java program without optional class

public class OptionalExample1 {

public static void main(String[] args) {

String[] str = new String[10];

String lowercaseString = str[5].toLowerCase();

System.out.print(lowercaseString);

}

output :

Exception in thread "main" java.lang.NullPointerException

at OptionalExample.main(OptionalExample.java:5)

Example2 :-Java program with optional class; if value is not present

import java.util.Optional;

public class OptionalExample2 {

public static void main(String[] args) {

String[] str = new String[10];

Optional<String> checkNull = Optional.ofNullable(str[5]);

// check for value is present or not

if(checkNull.isPresent()){

String lowercaseString = str[5].toLowerCase();

System.out.print(lowercaseString);

}else

System.out.println("string value is not present");

}

output :

string value is not present

Example3 :-Java program with optional class; if value is present

import java.util.Optional;

public class OptionalExample3{

public static void main(String[] args) {

String[] str = new String[10];

// Setting value for 5th index

str[5] = "JAVA OPTIONAL CLASS EXAMPLE....";

Optional<String> checkNull = Optional.ofNullable(str[5]);

// It Checks, value is present or not

if(checkNull.isPresent()){

String lowercaseString = str[5].toLowerCase();

System.out.print(lowercaseString);

}else

System.out.println("String value is not present");

}

output :

java optional class example....

Example4 :-

import java.util.Optional;

public class OptionalExample4 {

public static void main(String[] args) {

String[] str = new String[10];

// Setting value for 5th index

str[5] = "JAVA OPTIONAL CLASS EXAMPLE4";

Optional<String> checkNull = Optional.ofNullable(str[5]);

// printing value by using method reference

checkNull.ifPresent(System.out::println);

// printing value by using get method

System.out.println(checkNull.get());

System.out.println(str[5].toLowerCase());

}

output :

JAVA OPTIONAL CLASS EXAMPLE4

java optional class example4

6> Lambda Expression :-

Lambda expression is a new and important feature of Java which was included in Java SE 8. It provides a clear and concise way to represent one method interface using an expression. It is very useful in collection library. It helps to iterate, filter and extract data from collection. Before lambda expression, anonymous inner class was the only option to implement the method.

In other words, we can say it is a replacement of java inner anonymous class. Java lambda expression is treated as a function, so compiler does not create .class file.

or in other words, A lambda expression is an anonymous function that you can use to create delegates or expression tree types. By using lambda expression,you can write local functions that can be passed as arguments or returned as the value of function calls.

Why we use lambda expression ?

1>Less coding

2>It provides the implementations to functional interface.

Java Lambda expression Syntax :-

1. (argument-list) -> {body}

Java lambda expression is consisted of three components.

1) Argument-list: It can be empty or non-empty as well.

2) Arrow-token: It is used to link arguments-list and body of expression.

3) Body: It contains expressions and statements for lambda expression.

lets see...

1-A lambda expression can have zero, one or more parameters.

2-The type of the parameters can be explicitly declared or it can be inferred from the context. e.g. (String str) is same as just (str)

3-Parameters are enclosed in parentheses and separated by commas. e.g. (a, b) or (double d, int b) or (String str, int b, float f)

4-Empty parentheses are used to represent an empty set of parameters. e.g. () -> 102

5-When there is a single parameter, if its type is inferred, it is not mandatory to use parentheses. e.g. b -> return b*b

6-The body of the lambda expressions can contain zero, one or more statements.

7-If body of lambda expression has single statement curly brackets are not mandatory and the return type of the anonymous function is the same as that of the body expression.

8-When there is more than one statement in body than these must be enclosed in curly brackets (a code block) and the return type of the anonymous function is the same as the type of the value returned within the code block, or void if nothing is returned.

Java Functional Interfaces

Functional interface are nothing but, it is An interface with exactly one abstract method is known as Functional Interface, it is a Single Abstract Method interface(SAM interface).

A new annotation @FunctionalInterface has been introduced to mark an interface as Functional Interface. @FunctionalInterface annotation is a facility to avoid accidental addition of abstract methods in the functional interfaces. It’s optional but good practice to use it.

Functional interfaces are long awaited and much sought out feature of Java 8 because it enables us to use lambda expressions to instantiate them. A new package java.util.function with bunch of functional interfaces are added to provide target types for lambda expressions and method references. We will look into functional interfaces and lambda expressions in the future posts.

Note:- It is an anonymous function also. i.e. a function with no name

Example1 :-Java program without lambda expressions

interface CheckMoney{

public void check();

}

public class LambdaExpressionExample1 {

public static void main(String[] args) {

int numberOfNotes=10;

//without lambda, CheckMoney implementation

//using anonymous class

CheckMoney d=new CheckMoney(){

public void check(){System.out.println("Checking number of Notes is : "+numberOfNotes);}

};

d.check();

}

output :

Checking number of Notes is : 10

Example2 :-Java program with lambda expressions

interface CheckMoney{

public void check();

}

public class LambdaExpressionExample2 {

public static void main(String[] args) {

int numberOfNotes=10;

//with lambda, CheckMoney implementation

//using anonymous class

CheckMoney d=()->{

{System.out.println("Checking number of Notes is : "+numberOfNotes);}

};

d.check();

}

output :

Checking number of Notes is : 10

Example3 :-Java program lambda expressions : No Parameter

interface CheckMoney{

public String check();

}

public class LambdaExpressionExample3 {

public static void main(String[] args) {

//with lambda, CheckMoney implementation

//using anonymous class

CheckMoney d=()->{

return "I have nothing to check";

};

System.out.println(d.check());

}

output :

I have nothing to check

Example4 :-Java program lambda expressions : One Parameter

interface CheckMoney{

public String check(Integer numberofnotes);

}

public class LambdaExpressionExample4 {

public static void main(String[] args) {

//with lambda, CheckMoney implementation

//using anonymous class for single parameters

CheckMoney d=(Notes)->{

return "I have number of notes is : "+Notes;

};

System.out.println(d.check(40));

CheckMoney d1=(Notes)->{

return "I have number of notes is : "+Notes;

};

System.out.println(d1.check(120));

}

output :

I have number of notes is : 40

I have number of notes is : 120

Example4 :-Java program lambda expressions : One Parameter

interface Additions{

int add(int i,int j);

}

public class LambdaExpressionExample5{

public static void main(String[] args) {

// Multiple parameters in lambda expression

Additions ad1=(i,j)->(i+j);

System.out.println(ad1.add(11,12));

// Multiple parameters with data type in lambda expression

Additions ad2=(int i,int j)->(i+j);

System.out.println(ad2.add(13,120));

}

}

output :

133

Example6 :-Java program lambda expressions : with or without return statements

interface Additions{

int add(int i,int j);

}

public class LambdaExpressionExample6{

public static void main(String[] args) {

// Lambda expression without return statement.

Additions ad1=(i,j)->(i+j);

System.out.println(ad1.add(11,12));

// Lambda expression with return statement.

Additions ad2=(int i,int j)->{

return (i+j);

};

System.out.println(ad2.add(13,120));

}

output :

133

Example7 :-Java program lambda expressions : forEach() method

import java.util.*;

public class LambdaExpressionExample7{

public static void main(String[] args) {

List<String> list=new ArrayList<String>();

list.add("rani");

list.add("rekha");

list.add("roli");

list.add("rajni");

list.forEach(

(i)->System.out.println(i)

);

}

output :

rani

rekha

roli

rajni

Example8 :-Java program lambda expressions : Multiple Parameters

@FunctionalInterface

interface Sayable{

String say(String message);

}

public class LambdaExpressionExample8{

public static void main(String[] args) {

// You can pass multiple statements in lambda expression

Sayable person = (message)-> {

String str1 = "I would like to say, ";

String str2 = str1 + message;

return str2;

};

System.out.println(person.say("time is precious."));

}

output :

I would like to say, time is precious.

Example9 :-Java program lambda expressions : Creating Thread

public class LambdaExpressionExample9{

public static void main(String[] args) {

//Thread Example without lambda

Runnable r1=new Runnable(){

public void run(){

System.out.println("Thread1 is running...");

}

};

Thread t1=new Thread(r1);

t1.start();

//Thread Example with lambda

Runnable r2=()->{

System.out.println("Thread2 is running...");

};

Thread t2=new Thread(r2);

t2.start();

}

output :

Thread1 is running...

Thread2 is running...

Example10 :-Java program lambda expressions : Comparator

import java.util.ArrayList;

import java.util.Collections;

import java.util.List;

class Product{

int id;

String name;

float price;

public Product(int id, String name, float price) {

super();

this.id = id;

this.name = name;

this.price = price;

}

public class LambdaExpressionExample10{

public static void main(String[] args) {

List<Product> list=new ArrayList<Product>();

//Adding Products

list.add(new Product(1,"HP Laptop",25000f));

list.add(new Product(3,"Keyboard",300f));

list.add(new Product(2,"Dell Mouse",150f));

System.out.println("Sorting on the basis of name...");

// implementing lambda expression

Collections.sort(list,(p1,p2)->{

return p1.name.compareTo(p2.name);

});

for(Product p:list){

System.out.println(p.id+" "+p.name+" "+p.price);

}

System.out.println("Sorting on the basis of id...");

// implementing lambda expression

Collections.sort(list,(p1,p2)->{

return p1.id-p2.id;

});

for(Product p:list){

System.out.println(p.id+" "+p.name+" "+p.price);

}

System.out.println("Sorting on the basis of price...");

// implementing lambda expression

Collections.sort(list,(p1,p2)->{

return (int) (p1.price-p2.price);

});

for(Product p:list){

System.out.println(p.id+" "+p.name+" "+p.price);

}

output :

Sorting on the basis of name...

2 Dell Mouse 150.0

1 HP Laptop 25000.0

3 Keyboard 300.0

Sorting on the basis of id...

1 HP Laptop 25000.0

2 Dell Mouse 150.0

3 Keyboard 300.0

Sorting on the basis of price...

2 Dell Mouse 150.0

3 Keyboard 300.0

1 HP Laptop 25000.0

Example11 :-Java program lambda expressions : Filter Collection Data

import java.util.ArrayList;

import java.util.List;

import java.util.stream.Stream;

class Product{

int id;

String name;

float price;

public Product(int id, String name, float price) {

super();

this.id = id;

this.name = name;

this.price = price;

}

public class LambdaExpressionExample11{

public static void main(String[] args) {

List<Product> list=new ArrayList<Product>();

list.add(new Product(1,"Samsung A6",17000f));

list.add(new Product(3,"Iphone 6S",64000f));

list.add(new Product(2,"Sony Xperia",26000f));

list.add(new Product(4,"Nokia Lumia",10000f));

list.add(new Product(5,"Redmi3s ",26000f));

list.add(new Product(6,"Lenevo 6K power",21000f));

// using lambda to filter data

Stream<Product> filtered_data = list.stream().filter(p -> p.price > 20000);

System.out.println("Product price more then 20000");

// using lambda to iterate through collection

filtered_data.forEach(

product -> System.out.println(product.name+": "+product.price)

);

// using lambda to filter data

Stream<Product> filtered_data1 = list.stream().filter(p -> p.price > 40000);

System.out.println("Product price more then 40000");

// using lambda to iterate through collection

filtered_data1.forEach(

product -> System.out.println(product.name+": "+product.price)

);

}

output :

Product price more then 20000

Iphone 6S: 64000.0

Sony Xperia: 26000.0

Redmi3s : 26000.0

Lenevo 6K power: 21000.0

Product price more then 40000

Iphone 6S: 64000.0

Example12 :-Java program lambda expressions :Event Listener

import javax.swing.JButton;

import javax.swing.JFrame;

import javax.swing.JTextField;

public class LambdaExpressionExample12{

public static void main(String[] args) {

JTextField tf=new JTextField();

tf.setBounds(50, 50,150,20);

JButton b=new JButton("click me");

b.setBounds(80,100,70,20);

// lambda expression implementing here.

b.addActionListener(e-> {tf.setText("Hi first swing");});

JFrame f=new JFrame();

f.add(tf);f.add(b);

f.setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE);

f.setLayout(null);

f.setSize(300, 200);

f.setVisible(true);

}

output :

7> Method Reference :-

Method reference is used to refer method of functional interface. It is compact and easy form of lambda expression. Each time when you are using lambda expression to just referring a method, you can replace your lambda expression with method reference.

In other words-

Instead of using An ANONYMOUS CLASS

we can use A LAMBDA EXPRESSION

if it is for only one method, we can use A METHOD REFERENCE

There are four type of method reference :-

1> A method reference to a static method

2> A method Reference to a constructor

3> A method Reference to an instance method of an object of a particular type

4> A method reference to an instance method of an existing object

1> Reference to a static method

we have lambda expression like :-

(args) - >Class.staticMethod(args)

but it convert by method reference like this :-

Class :: staticMethod

You can see that between a static method and a static method reference, instead of the . operator, we use the :: operator, and that we don't pass arguments to the method reference.

In general, we don't need to pass arguments to method references. However, arguments are treated depending on type of method reference.

In this case, any arguments (if any) taken by the method are passed automatically behind the curtains.

Syntax :

ClassName :: staticMethodName

import java.util.function.BiFunction;

class Math{

public static int add(int a, int b){

return a+b;

}

public class MethodReference01 {

public static void main(String[] args) {

BiFunction<Integer, Integer, Integer>adder = Math::add;

int result = adder.apply(10, 20);

System.out.println(result);

}

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Java 8 New Feature

Tuesday, 22 August 2017