Hello everyone today i am sharing about Java 8 Some features that can improve our productivity and reduce our execution time
1. Lambda expressions
2. ForEach() method
3. Method references
4. Functional interfaces
5. Stream API
6. Optional class
7. Parallel sort
8. Date and Time
Lambda Expressions :
Lambda expression helps us to write our code in a functional style. It provides a clear way a help using an expression.
It is very useful in a collection library in which it helps to iterate, filter and extract data.
Example:
public class LambdaExprEx{
public static void main(String[] args) {
List<String> list=new ArrayList<String>();
list.add("Rajashekar");
list.add("Chinnu");
list.add("Rohit");
list.add("Hello");
list.add("Java");
list.forEach((n)->System.out.println(n));
}
}
OUTPUT :-
Rajashekar
Chinnu
Rohit
Hello
Java
Example 2:
public static void main(String[] args) {
// TODO Auto-generated method stub
InterfaceA a1=()-> System.out.println("m1 method");
a1.m1();
InterfaceB b1=(a,b,c)->
{
System.out.println(a+b+c);
};
b1.m2(10,20,30);
InterfaceC c1=(int a,int b)->
{
if(a<b)
{
return a;
}
else
{
return b;
}
};
int min=c1.m3(100,200);
System.out.println("Minimum"+min);
InterfaceD d1=(int a,int b)->
{
for(int i=a;i<=b;i++)
{
System.out.println(i);
}
};
d1.m4(1,10);
}
}
public interface InterfaceD {
void m4(int a,int b);
}
public interface InterfaceC {
int m3(int a,int b);
}
public interface InterfaceB {
void m2(int a,int b,int c);
}
public interface InterfaceA {
void m1();
}
output:
m1 method
60
Minimum100
1
2
3
4
5
6
7
8
9
10
ForEach() method : -
Java provides a new method forEach() to iterate the elements. It is defined in the Iterable and Stream interface.
public class ForEachExample {
public static void main(String[] args) {
List<String> list= new ArrayList<String>();
list.add("ABC");
list.add("XYZ");
list.add("Java");
list.add("Hello");
list.add("World");
System.out.println("------------Iterating by passing method reference---------------");
list.forEach(System.out::println);
}
}
output:-
------------Iterating by passing method reference---------------
ABC
XYZ
Java
Hello
World
Java SteamAPI: -
it used to perform operations on streams and manipulate the data .it take input from collection frame classes. it won't store any data.
| consumer | void accept(T t) | accepts one argument | it won't return anything |
| predicate | boolean test(T t) | accepts one argument | true or false |
| function | R apply(T t) | accepts one argument | return some value |
| supplier | T get() | zero | returns some value |
import java.util.Arrays;
import java.util.Comparator;
import java.util.List;
import java.util.Optional;
import java.util.stream.Stream;
public class ClassStreamAPI
{
public static void main(String[] args)
{
Stream<String> s1=Stream.empty();
List<Integer> l1=Arrays.asList(1,2,3,4,5);
Stream<Integer> s2=l1.stream();
s2.forEach(ele->System.out.println(ele));
System.out.println("========================");
l1.stream().filter(x->x%2==0).forEach(ele->System.out.println(ele));
System.out.println("========================");
l1.stream().filter(x->x%2!=0).map(x->x*10).forEach(ele->System.out.println(ele));
System.out.println("========================");
List<Integer> l2=Arrays.asList(5,2,2,1,2,6,3,6,4,5);
Stream<Integer> s3=l2.stream();
s3.distinct().sorted().forEach(ele->System.out.println(ele));
System.out.println("========================");
l2.stream().distinct().sorted(Comparator.reverseOrder()).forEach(ele->System.out.println(ele));
System.out.println("========================");
long c=l2.stream().distinct().count();
System.out.println(c);
System.out.println("========================");
boolean b=l2.stream().allMatch(x->x>1);
System.out.println(b);
System.out.println("========================");
boolean b1=l2.stream().anyMatch(x->x>3);
System.out.println(b1);
System.out.println("========================");
boolean b2=l2.stream().noneMatch(x->x>1);
System.out.println(b2);
int sum= l1.stream().reduce(0,(p,q)->p+q);
System.out.println(sum);
}
}
output:
1
2
3
4
5
=======================================
2
4
========================================
10
30
50
========================================
1
2
3
4
5
6
========================================
6
5
4
3
2
1
========================================
6
========================================
false
========================================
true
========================================
true
========================================
false
========================================
15
Date/Time API:-
Java has introduced a new Date and Time API since Java 8. The java.time package contains Java 8 Date and Time classes.
import java.time.LocalTime;
import java.time.ZoneId;
import java.time.ZonedDateTime;
import java.util.Arrays;
public class ClassDate {
public static void main(String[] args) {
// TODO Auto-generated method stub
System.out.println(ZonedDateTime.now());
System.out.println(ZoneId.getAvailableZoneIds());
System.out.println(LocalTime.now(ZoneId.of("America/Los_Angeles")));
System.out.println(LocalTime.now(ZoneId.of("America/New_York")));
System.out.println(LocalTime.now(ZoneId.of("Asia/Kolkata")));
}
}
output:
2023-10-04T13:29:12.504+05:30[Asia/Calcutta]
[Asia/Aden, America/Cuiaba, Etc/GMT+9, Etc/GMT+8, Africa/Nairobi, America/Marigot, Asia/Aqtau, Pacific/Kwajalein, America/El_Salvador, Asia/Pontianak, Africa/Cairo, Pacific/Pago_Pago, Africa/Mbabane, Asia/Kuching, Pacific/Honolulu, Pacific/Rarotonga, America/Guatemala, Australia/Hobart, Europe/London, America/Belize, America/Panama, Asia/Chungking, America/Managua, America/Indiana/Petersburg, Asia/Yerevan, Europe/Brussels, GMT, Europe/Warsaw, America/Chicago, Asia/Kashgar, Chile/Continental, Pacific/Yap, CET, Etc/GMT-1, Etc/GMT-0, Europe/Jersey, America/Tegucigalpa, Etc/GMT-5, Europe/Istanbul, America/Eirunepe, Etc/GMT-4, America/Miquelon, Etc/GMT-3, Europe/Luxembourg, Etc/GMT-2, Etc/GMT-9, America/Argentina/Catamarca, Etc/GMT-8, Etc/GMT-7, Etc/GMT-6, Europe/Zaporozhye, Canada/Yukon, Canada/Atlantic, Atlantic/St_Helena, Australia/Tasmania, Libya, Europe/Guernsey, America/Grand_Turk, US/Pacific-New, Asia/Samarkand, America/Argentina/Cordoba, Asia/Phnom_Penh, Africa/Kigali, Asia/Almaty, US/Alaska, Asia/Dubai, Europe/Isle_of_Man, America/Araguaina, Cuba, Asia/Novosibirsk, America/Argentina/Salta, Etc/GMT+3, Africa/Tunis, Etc/GMT+2, Etc/GMT+1, Pacific/Fakaofo, Africa/Tripoli, Etc/GMT+0, Israel, Africa/Banjul, Etc/GMT+7, Indian/Comoro, Etc/GMT+6, Etc/GMT+5, Etc/GMT+4, Pacific/Port_Moresby, US/Arizona, Antarctica/Syowa, Indian/Reunion, Pacific/Palau, Europe/Kaliningrad, America/Montevideo, Africa/Windhoek, Asia/Karachi, Africa/Mogadishu, Australia/Perth, Brazil/East, Etc/GMT, Asia/Chita, Pacific/Easter, Antarctica/Davis, Antarctica/McMurdo, Asia/Macao, America/Manaus, Africa/Freetown, Europe/Bucharest, America/Argentina/Mendoza, Asia/Macau, Europe/Malta, Mexico/BajaSur, Pacific/Tahiti, Africa/Asmera, Europe/Busingen, America/Argentina/Rio_Gallegos, Africa/Malabo, Europe/Skopje, America/Catamarca, America/Godthab, Europe/Sarajevo, Australia/ACT, GB-Eire, Africa/Lagos, America/Cordoba, Europe/Rome, Asia/Dacca, Indian/Mauritius, Pacific/Samoa, America/Regina, America/Fort_Wayne, America/Dawson_Creek, Africa/Algiers, Europe/Mariehamn, America/St_Johns, America/St_Thomas, Europe/Zurich, America/Anguilla, Asia/Dili, America/Denver, Africa/Bamako, GB, Mexico/General, Pacific/Wallis, Europe/Gibraltar, Africa/Conakry, Africa/Lubumbashi, Asia/Istanbul, America/Havana, NZ-CHAT, Asia/Choibalsan, America/Porto_Acre, Asia/Omsk, Europe/Vaduz, US/Michigan, Asia/Dhaka, America/Barbados, Europe/Tiraspol, Atlantic/Cape_Verde, Asia/Yekaterinburg, America/Louisville, Pacific/Johnston, Pacific/Chatham, Europe/Ljubljana, America/Sao_Paulo, Asia/Jayapura, America/Curacao, Asia/Dushanbe, America/Guyana, America/Guayaquil, America/Martinique, Portugal, Europe/Berlin, Europe/Moscow, Europe/Chisinau, America/Puerto_Rico, America/Rankin_Inlet, Pacific/Ponape, Europe/Stockholm, Europe/Budapest, America/Argentina/Jujuy, Australia/Eucla, Asia/Shanghai, Universal, Europe/Zagreb, America/Port_of_Spain, Europe/Helsinki, Asia/Beirut, Asia/Tel_Aviv, Pacific/Bougainville, US/Central, Africa/Sao_Tome, Indian/Chagos, America/Cayenne, Asia/Yakutsk, Pacific/Galapagos, Australia/North, Europe/Paris, Africa/Ndjamena, Pacific/Fiji, America/Rainy_River, Indian/Maldives, Australia/Yancowinna, SystemV/AST4, Asia/Oral, America/Yellowknife, Pacific/Enderbury, America/Juneau, Australia/Victoria, America/Indiana/Vevay, Asia/Tashkent, Asia/Jakarta, Africa/Ceuta, America/Recife, America/Buenos_Aires, America/Noronha, America/Swift_Current, Australia/Adelaide, America/Metlakatla, Africa/Djibouti, America/Paramaribo, Europe/Simferopol, Europe/Sofia, Africa/Nouakchott, Europe/Prague, America/Indiana/Vincennes, Antarctica/Mawson, America/Kralendijk, Antarctica/Troll, Europe/Samara, Indian/Christmas, America/Antigua, Pacific/Gambier, America/Indianapolis, America/Inuvik, America/Iqaluit, Pacific/Funafuti, UTC, Antarctica/Macquarie, Canada/Pacific, America/Moncton, Africa/Gaborone, Pacific/Chuuk, Asia/Pyongyang, America/St_Vincent, Asia/Gaza, Etc/Universal, PST8PDT, Atlantic/Faeroe, Asia/Qyzylorda, Canada/Newfoundland, America/Kentucky/Louisville, America/Yakutat, Asia/Ho_Chi_Minh, Antarctica/Casey, Europe/Copenhagen, Africa/Asmara, Atlantic/Azores, Europe/Vienna, ROK, Pacific/Pitcairn, America/Mazatlan, Australia/Queensland, Pacific/Nauru, Europe/Tirane, Asia/Kolkata, SystemV/MST7, Australia/Canberra, MET, Australia/Broken_Hill, Europe/Riga, America/Dominica, Africa/Abidjan, America/Mendoza, America/Santarem, Kwajalein, America/Asuncion, Asia/Ulan_Bator, NZ, America/Boise, Australia/Currie, EST5EDT, Pacific/Guam, Pacific/Wake, Atlantic/Bermuda, America/Costa_Rica, America/Dawson, Asia/Chongqing, Eire, Europe/Amsterdam, America/Indiana/Knox, America/North_Dakota/Beulah, Africa/Accra, Atlantic/Faroe, Mexico/BajaNorte, America/Maceio, Etc/UCT, Pacific/Apia, GMT0, America/Atka, Pacific/Niue, Canada/East-Saskatchewan, Australia/Lord_Howe, Europe/Dublin, Pacific/Truk, MST7MDT, America/Monterrey, America/Nassau, America/Jamaica, Asia/Bishkek, America/Atikokan, Atlantic/Stanley, Australia/NSW, US/Hawaii, SystemV/CST6, Indian/Mahe, Asia/Aqtobe, America/Sitka, Asia/Vladivostok, Africa/Libreville, Africa/Maputo, Zulu, America/Kentucky/Monticello, Africa/El_Aaiun, Africa/Ouagadougou, America/Coral_Harbour, Pacific/Marquesas, Brazil/West, America/Aruba, America/North_Dakota/Center, America/Cayman, Asia/Ulaanbaatar, Asia/Baghdad, Europe/San_Marino, America/Indiana/Tell_City, America/Tijuana, Pacific/Saipan, SystemV/YST9, Africa/Douala, America/Chihuahua, America/Ojinaga, Asia/Hovd, America/Anchorage, Chile/EasterIsland, America/Halifax, Antarctica/Rothera, America/Indiana/Indianapolis, US/Mountain, Asia/Damascus, America/Argentina/San_Luis, America/Santiago, Asia/Baku, America/Argentina/Ushuaia, Atlantic/Reykjavik, Africa/Brazzaville, Africa/Porto-Novo, America/La_Paz, Antarctica/DumontDUrville, Asia/Taipei, Antarctica/South_Pole, Asia/Manila, Asia/Bangkok, Africa/Dar_es_Salaam, Poland, Atlantic/Madeira, Antarctica/Palmer, America/Thunder_Bay, Africa/Addis_Ababa, Europe/Uzhgorod, Brazil/DeNoronha, Asia/Ashkhabad, Etc/Zulu, America/Indiana/Marengo, America/Creston, America/Mexico_City, Antarctica/Vostok, Asia/Jerusalem, Europe/Andorra, US/Samoa, PRC, Asia/Vientiane, Pacific/Kiritimati, America/Matamoros, America/Blanc-Sablon, Asia/Riyadh, Iceland, Pacific/Pohnpei, Asia/Ujung_Pandang, Atlantic/South_Georgia, Europe/Lisbon, Asia/Harbin, Europe/Oslo, Asia/Novokuznetsk, CST6CDT, Atlantic/Canary, America/Knox_IN, Asia/Kuwait, SystemV/HST10, Pacific/Efate, Africa/Lome, America/Bogota, America/Menominee, America/Adak, Pacific/Norfolk, America/Resolute, Pacific/Tarawa, Africa/Kampala, Asia/Krasnoyarsk, Greenwich, SystemV/EST5, America/Edmonton, Europe/Podgorica, Australia/South, Canada/Central, Africa/Bujumbura, America/Santo_Domingo, US/Eastern, Europe/Minsk, Pacific/Auckland, Africa/Casablanca, America/Glace_Bay, Canada/Eastern, Asia/Qatar, Europe/Kiev, Singapore, Asia/Magadan, SystemV/PST8, America/Port-au-Prince, Europe/Belfast, America/St_Barthelemy, Asia/Ashgabat, Africa/Luanda, America/Nipigon, Atlantic/Jan_Mayen, Brazil/Acre, Asia/Muscat, Asia/Bahrain, Europe/Vilnius, America/Fortaleza, Etc/GMT0, US/East-Indiana, America/Hermosillo, America/Cancun, Africa/Maseru, Pacific/Kosrae, Africa/Kinshasa, Asia/Kathmandu, Asia/Seoul, Australia/Sydney, America/Lima, Australia/LHI, America/St_Lucia, Europe/Madrid, America/Bahia_Banderas, America/Montserrat, Asia/Brunei, America/Santa_Isabel, Canada/Mountain, America/Cambridge_Bay, Asia/Colombo, Australia/West, Indian/Antananarivo, Australia/Brisbane, Indian/Mayotte, US/Indiana-Starke, Asia/Urumqi, US/Aleutian, Europe/Volgograd, America/Lower_Princes, America/Vancouver, Africa/Blantyre, America/Rio_Branco, America/Danmarkshavn, America/Detroit, America/Thule, Africa/Lusaka, Asia/Hong_Kong, Iran, America/Argentina/La_Rioja, Africa/Dakar, SystemV/CST6CDT, America/Tortola, America/Porto_Velho, Asia/Sakhalin, Etc/GMT+10, America/Scoresbysund, Asia/Kamchatka, Asia/Thimbu, Africa/Harare, Etc/GMT+12, Etc/GMT+11, Navajo, America/Nome, Europe/Tallinn, Turkey, Africa/Khartoum, Africa/Johannesburg, Africa/Bangui, Europe/Belgrade, Jamaica, Africa/Bissau, Asia/Tehran, WET, Africa/Juba, America/Campo_Grande, America/Belem, Etc/Greenwich, Asia/Saigon, America/Ensenada, Pacific/Midway, America/Jujuy, Africa/Timbuktu, America/Bahia, America/Goose_Bay, America/Virgin, America/Pangnirtung, Asia/Katmandu, America/Phoenix, Africa/Niamey, America/Whitehorse, Pacific/Noumea, Asia/Tbilisi, America/Montreal, Asia/Makassar, America/Argentina/San_Juan, Hongkong, UCT, Asia/Nicosia, America/Indiana/Winamac, SystemV/MST7MDT, America/Argentina/ComodRivadavia, America/Boa_Vista, America/Grenada, Australia/Darwin, Asia/Khandyga, Asia/Kuala_Lumpur, Asia/Thimphu, Asia/Rangoon, Europe/Bratislava, Asia/Calcutta, America/Argentina/Tucuman, Asia/Kabul, Indian/Cocos, Japan, Pacific/Tongatapu, America/New_York, Etc/GMT-12, Etc/GMT-11, Etc/GMT-10, SystemV/YST9YDT, Etc/GMT-14, Etc/GMT-13, W-SU, America/Merida, EET, America/Rosario, Canada/Saskatchewan, America/St_Kitts, Arctic/Longyearbyen, America/Fort_Nelson, America/Caracas, America/Guadeloupe, Asia/Hebron, Indian/Kerguelen, SystemV/PST8PDT, Africa/Monrovia, Asia/Ust-Nera, Egypt, Asia/Srednekolymsk, America/North_Dakota/New_Salem, Asia/Anadyr, Australia/Melbourne, Asia/Irkutsk, America/Shiprock, America/Winnipeg, Europe/Vatican, Asia/Amman, Etc/UTC, SystemV/AST4ADT, Asia/Tokyo, America/Toronto, Asia/Singapore, Australia/Lindeman, America/Los_Angeles, SystemV/EST5EDT, Pacific/Majuro, America/Argentina/Buenos_Aires, Europe/Nicosia, Pacific/Guadalcanal, Europe/Athens, US/Pacific, Europe/Monaco]
00:59:12.559
03:59:12.644
13:29:12.645
Java Parallel Array Sorting
Java provides a new additional feature in Arrays class which is used to sort array elements parallelly.
The parallelSort() method has added to java.util.Arrays class that uses the JSR 166 Fork/Join parallelism common pool to provide sorting of arrays.
It is an overloaded method.
import java.util.Arrays;
public class ClassParallelSort {
public static void main(String[] args) {
// TODO Auto-generated method stub
int[] a1={1,7,2,4,9,8,5,2};
/*Arrays.sort(a1);
System.out.println(Arrays.toString(a1));*/
Arrays.parallelSort(a1,0,4);
System.out.println(Arrays.toString(a1));
System.out.println("==================================");
Arrays.parallelSort(a1,3,8);
System.out.println(Arrays.toString(a1));
}
}
output:-
[1, 2, 4, 7, 9, 8, 5, 2]
==================================
[1, 2, 4, 2, 5, 7, 8, 9]
Optional class
Java introduced a new class Optional in Java 8. It is a public final class which is used to deal with NullPointerException in Java application.
We must import java.util package to use this class. It provides methods to check the presence of value for particular variable.
import java.util.Optional;
public class ClassOptional {
public static void main(String[] args) {
// TODO Auto-generated method stub
String s=null;
//System.out.println(s.length());
String[] s2=new String[10];
//System.out.println(s2[6].length());
s2[7]="abc";
Optional<Integer> o1=Optional.empty();
System.out.println(o1);
Optional<String> o2=Optional.ofNullable(s2[6]);
System.out.println(o2);
if(o2.isPresent())
{
System.out.println(s2[6].length());
}
else
{
System.out.println("empty String");
}
}
}
output:-
Optional.empty
Optional.empty
empty String
Functional Interface
An Interface that contains only one abstract method is known as functional interface. It can have any number of default and static methods. It can also declare methods of object class.
Functional interfaces are also known as Single Abstract Method Interfaces (SAM Interfaces).
@FunctionalInterface
interface running{
void run(String msg);
}
public class Functional implements running{
public void run(String msg){
System.out.println(msg);
}
public static void main(String[] args) {
Functional f = new Functional();
f.run("Hi Functional interface");
}
}
output:-
Hi Functional interface
Method References
Java 8 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.
@FunctionalInterface
public interface InterfaceD
{
void meth2();
}
public class ClassMethodReference2
{
void show()
{
System.out.println("Method reference- Non-static method");
}
static void show2()
{
System.out.println("Method reference- static method");
}
ClassMethodReference2()
{
System.out.println("Method reference- Constructor");
}
}
public class ClassMethodReference
{
void fun()
{
//InterfaceD p= new ClassMethodReference2()::show; //non-static method
//InterfaceD p=ClassMethodReference2::show2;
InterfaceD p=ClassMethodReference2::new;
p.meth2();
}
public static void main(String[] args)
{
ClassMethodReference m1=new ClassMethodReference();
m1.fun();
}
}
output:-
method refence non static method