Some important features of java 8 are listed below-
- forEach() method in Iterable interface
- default and static methods in Interfaces
- Lambda Expressions
- Java Time API
- Java Stream API for Bulk Data Operations on Collections
1. forEach using Map and List interface
EXAMPLE-
import java.util.ArrayList;
import java.util.HashMap;
import java.util.List;
import java.util.Map;
public class Java8Feature {
public static void main(String[] args) {
// TODO Auto-generated method stub
Java8Feature obj = new Java8Feature();
System.out.println("*** forEach with Map ***");
obj.myMapIterator();
System.out.println("*** forEach with List ***");
obj.myListIterator();
}
void myMapIterator() {
Map<String, Integer> items = new HashMap<>();
items.put("A", 10);
items.put("B", 20);
items.put("C", 30);
items.put("D", 40);
items.put("E", 50);
items.put("F", 60);
//1. Filter map using normal way
for (Map.Entry<String, Integer> entry : items.entrySet()) {
System.out.println("Item : " + entry.getKey() +" Count : "+ entry.getValue());
}
//2. Filter map using Lambda expression
items.forEach((k, v) -> System.out.println("Item : " +k +" Count : " + v));
//3. Filter map using Lambda expression
items.forEach((k, v) -> {
System.out.println("Item : " + k +" Count : " + v);
if ("E".equals(k)) {
System.out.println("Hello E");
}
});
}
void myListIterator() {
List<String> items = new ArrayList<>();
items.add("A");
items.add("B");
items.add("C");
items.add("D");
//1. Filter list using normal way
for (String string : items) {
System.out.println("Item : " + string);
}
//2. Filter list using Lambda expression
items.forEach(sanjay -> System.out.println(sanjay));
//3. Filter list using Lambda expression
items.forEach(aaa -> {
if ("C".equals(aaa)) {
System.out.println("Lambda expression");
}
});
//4. Filter using method reference
items.forEach(System.out::print);
// Work like below
//items.forEach(i-> System.out.println(i));
//5. Stream and filter
items.stream()
.filter(s->s.contains("B"))
.forEach(System.out::println);
}
}
2. default and static methods in Interfaces
}
2. default and static methods in Interfaces
default method of java 8 gives a flexibility to modify or add new upcoming feature in future on existing interface. default method does not effect to all other implementer classes if something is changed on default method, because default method is optional for exiting implementer classes to use default method even not need to override it by all implementer classes.
default method does not create ambiguity if 2 interface having same default method name. its is accessed via interface name.
EXAMPLE-
public class Java8InterfaceDefaultMethod implements IConsumerUpdate ,IMarketProduct ,IMarketInventry{
public static void main(String[] args) {
// TODO Auto-generated method stub
Java8InterfaceDefaultMethod obj = new Java8InterfaceDefaultMethod();
int saleCount = obj.getProductSaleCount(10);
System.out.println("Product sale count : " + saleCount);
String pName = obj.getProductName();
System.out.println("Product Name : " + pName);
obj.getConsumer();
String pQuality=IMarketProduct.getProductQuality();
System.out.println("product quality : " +pQuality);
}
@Override
public int getProductSaleCount(int saleCount) {
// TODO Auto-generated method stub
return saleCount;
}
@Override
public int getInventryCount() {
// TODO Auto-generated method stub
return 0;
}
}
interface IMarketProduct {
String productName = "MacBook pro";
String productQuality = "Normal";
int getProductSaleCount(int count);
default String getProduct() {
return productName;
}
static String getProductQuality() {
return productQuality;
}
}
interface IMarketInventry {
String name = "Windows laptop";
int getInventryCount();
default String getProductName() {
return name;
}
}
interface IConsumerUpdate {
default void getConsumer() {
System.out.println("I am Consumer");
}
}
3. Lambda Expressions
3. Lambda Expressions
public class ThreadEvenOdd {
int inputNum=13;
public ThreadEvenOdd(int a) {
super();
this.inputNum = a;
}
public static boolean checkPrime(int n) {
for (int i = 2; i < n; i++) {
if (n % i == 0)
return false;
}
return true;
}
public static void main(String[] args) {
// TODO Auto-generated method stub
int inputNumber=13;
ThreadEvenOdd obj = new ThreadEvenOdd(inputNumber);
/**
* Using Lambda expression introduced in java 8
*/
Runnable runnable = () -> {
// TODO Auto-generated method stub
for (int i = 0; i < obj.inputNum; i++) {
try {
if (i % 2 == 0) {
System.out.println("Even nuber is: " + i);
}
Thread.sleep(0);
} catch (InterruptedException e) {
// TODO Auto-generated catch block
e.printStackTrace();
}
}
};
/**
* using java 7
*/
Runnable runnable2 = new Runnable() {
@Override
public void run() {
// TODO Auto-generated method stub
for (int i = 0; i < obj.inputNum; i++) {
try {
if (i % 2 != 0) {
System.out.println("odd nuber is: " + i);
}
Thread.sleep(0);
} catch (Exception e) {
e.getMessage();
}
}
}
};
/**
* Using Lambda expression introduced in java 8
*/
Runnable runnable3 = () -> {
// TODO Auto-generated method stub
for (int i = 2; i < obj.inputNum; i++) {
if (checkPrime(i)) {
System.out.println("Prime number " + i);
}
}
};
Thread t = new Thread(runnable);
Thread t1 = new Thread(runnable2);
Thread t2 = new Thread(runnable3);
t.start();
t1.start();
t2.start();
}
}
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