import java.time.LocalDate; import java.time.Month; import java.time.format.DateTimeFormatter; import java.time.temporal.ChronoUnit; class Tester { public static void main(String[] args) { // To print today's date which function should I use ? //LocalDate provides the output in the form of YYYY-MM-DD LocalDate today = LocalDate.now(); //Invoking the static now() will return the current date from the system clock System.out.println(today); /* * To display any date in default format we use of() method. * of() takes parameters as public static LocalDate of(int year,Month month,int dayOfMonth)(where Month is enum ) * Or public static LocalDate of(int year,int month,int dayOfMonth) * This returns a LocalDate with the specified year, month and day-of-month */ System.out.println(); System.out.println("************"+"of()"+"************"); System.out.println("LocalDate.of(2018, 8, 29) :- "+LocalDate.of(2018, 8, 29)); System.out.println("LocalDate.of(2017,Month.APRIL, 29) :- "+LocalDate.of(2017,Month.APRIL, 29)); /* To access the date information we have certain methods like getYear(),getMonth(),getDayOfMonth() etc. */ System.out.println(); System.out.println("***********DateTimeFormater***********"); LocalDate date = LocalDate.parse("13 Feb, 2020", DateTimeFormatter.ofPattern("dd MMM, yyyy")); System.out.println(date.format(DateTimeFormatter.ofPattern("dd-MMM-yyyy"))); System.out.println("Input Format is 13 Feb, 2020 \nOutput Format :- "+date); /* .format() method formats the date according to user defined pattern. */ String dateString = date.format(DateTimeFormatter.ofPattern("dd/MMM/uuuu")); System.out.println(dateString); /* The DateTimeFormatter class in Java is used for parsing dates in different formats. ofPattern method will create a formatter based on the pattern given by the programmer. For example, d MMM yyyy will format 2011-12-03 as '3 Dec 2011'. */ System.out.println(); System.out.println("************"+"Functions to access date information"+"************"); System.out.println("Today's Date :- "+LocalDate.now()); System.out.println("Month in Today's Date :- "+LocalDate.now().getMonth()); System.out.println("What is the current year going on .... ? :- "+LocalDate.now().getYear()); System.out.println("Which day is today ? :- "+LocalDate.now().getDayOfWeek()); /* getDayOfWeek() & getMonth() :- returns an enum instead of int value. To get int value, we can use getValue() methods Try :- System.out.println("Month in Today's Date :- "+LocalDate.now().getMonth().getValue()); System.out.println("Which day is today ? :- "+LocalDate.now().getDayOfWeek().getValue()); */ /* Following are methods for localdate calculations plusDays(),plusWeeks(),plusMonths(),plusYears(),minusDays(),minusWeeks(),minusMonths,()minusYears() All of these methods take parameters having Long datatype */ System.out.println(); System.out.println("************"+"LocalDate Calculations"+"************"); System.out.println("Today's Date :- "+LocalDate.now()); System.out.println("Date after 7 days ? => "+LocalDate.now().plusDays(7)); System.out.println("Date after 7 months ? => "+LocalDate.now().plusMonths(7)); System.out.println("Date after 7 Years ? => "+LocalDate.now().plusYears(7)); System.out.println("Date after 7 weeks ? => "+LocalDate.now().plusWeeks(7)); System.out.println(); /* Try :- Find the date 20 days ago and 4 months ago and 40 years ago */ System.out.println(); System.out.println("************"+"Difference using ChronoUnit"+"************"); LocalDate dateObj = LocalDate.of(1997, Month.FEBRUARY, 15); System.out.println("Difference Between dateObj and today's date in number of Years"); System.out.println(ChronoUnit.YEARS.between(dateObj, LocalDate.now())); // Calculate the number of days between dateObj and today's date /* We can also modify the date using ChronoUnit */ System.out.println(); System.out.println("Modification of date using ChronoUnit :- "); System.out.println("Today's date :- "+LocalDate.now()); System.out.println("Date After 5 days :- "+LocalDate.now().plus(5,ChronoUnit.DAYS)); //Try adding months and years in the current date. System.out.println(); System.out.println("until() with ChronoUnit"); LocalDate todayObj = LocalDate.now(); LocalDate date1 = LocalDate.of(2014,5,25); System.out.println("Difference between todayObj and date1(in terms of Number of Days) :- "+date1.until(todayObj,ChronoUnit.DAYS)); //calulcate the difference in terms of months and years /* To Compare two dates we also have compareTo() method Method Signature of compareTo() :- int compareTo(chronoLocalDate date) It returns the value 0 if the argument Date is equal to this Date. It returns a value less than 0 if this Date is before the Date argument. It returns a value greater than 0 if this Date is after the Date argument. Try Comparing today's date with date1 using compareTo() */ System.out.println(); System.out.println("************"+"isAfter() and isBefore()"+"************"); LocalDate dateFirst = LocalDate.of(2018, 2,21); LocalDate dateSecond = LocalDate.of(2018, 2,20); System.out.println("dateFirst.isBefore(dateSecond) :- "+dateFirst.isBefore(dateSecond)); System.out.println("dateFirst.isAfter(dateSecond) :- "+dateFirst.isAfter(dateSecond)); } }
Write, Run & Share Java code online using OneCompiler's Java online compiler for free. It's one of the robust, feature-rich online compilers for Java language, running the Java LTS version 17. Getting started with the OneCompiler's Java editor is easy and fast. The editor shows sample boilerplate code when you choose language as Java and start coding.
OneCompiler's Java online editor supports stdin and users can give inputs to the programs using the STDIN textbox under the I/O tab. Using Scanner class in Java program, you can read the inputs. Following is a sample program that shows reading STDIN ( A string in this case ).
import java.util.Scanner;
class Input {
public static void main(String[] args) {
Scanner input = new Scanner(System.in);
System.out.println("Enter your name: ");
String inp = input.next();
System.out.println("Hello, " + inp);
}
}
OneCompiler supports Gradle for dependency management. Users can add dependencies in the build.gradle
file and use them in their programs. When you add the dependencies for the first time, the first run might be a little slow as we download the dependencies, but the subsequent runs will be faster. Following sample Gradle configuration shows how to add dependencies
apply plugin:'application'
mainClassName = 'HelloWorld'
run { standardInput = System.in }
sourceSets { main { java { srcDir './' } } }
repositories {
jcenter()
}
dependencies {
// add dependencies here as below
implementation group: 'org.apache.commons', name: 'commons-lang3', version: '3.9'
}
Java is a very popular general-purpose programming language, it is class-based and object-oriented. Java was developed by James Gosling at Sun Microsystems ( later acquired by Oracle) the initial release of Java was in 1995. Java 17 is the latest long-term supported version (LTS). As of today, Java is the world's number one server programming language with a 12 million developer community, 5 million students studying worldwide and it's #1 choice for the cloud development.
short x = 999; // -32768 to 32767
int x = 99999; // -2147483648 to 2147483647
long x = 99999999999L; // -9223372036854775808 to 9223372036854775807
float x = 1.2;
double x = 99.99d;
byte x = 99; // -128 to 127
char x = 'A';
boolean x = true;
When ever you want to perform a set of operations based on a condition If-Else is used.
if(conditional-expression) {
// code
} else {
// code
}
Example:
int i = 10;
if(i % 2 == 0) {
System.out.println("i is even number");
} else {
System.out.println("i is odd number");
}
Switch is an alternative to If-Else-If ladder and to select one among many blocks of code.
switch(<conditional-expression>) {
case value1:
// code
break; // optional
case value2:
// code
break; // optional
...
default:
//code to be executed when all the above cases are not matched;
}
For loop is used to iterate a set of statements based on a condition. Usually for loop is preferred when number of iterations is known in advance.
for(Initialization; Condition; Increment/decrement){
//code
}
While is also used to iterate a set of statements based on a condition. Usually while is preferred when number of iterations are not known in advance.
while(<condition>){
// code
}
Do-while is also used to iterate a set of statements based on a condition. It is mostly used when you need to execute the statements atleast once.
do {
// code
} while (<condition>);
Class is the blueprint of an object, which is also referred as user-defined data type with variables and functions. Object is a basic unit in OOP, and is an instance of the class.
class
keyword is required to create a class.
class Mobile {
public: // access specifier which specifies that accessibility of class members
string name; // string variable (attribute)
int price; // int variable (attribute)
};
Mobile m1 = new Mobile();
public class Greeting {
static void hello() {
System.out.println("Hello.. Happy learning!");
}
public static void main(String[] args) {
hello();
}
}
Collection is a group of objects which can be represented as a single unit. Collections are introduced to bring a unified common interface to all the objects.
Collection Framework was introduced since JDK 1.2 which is used to represent and manage Collections and it contains:
This framework also defines map interfaces and several classes in addition to Collections.
Collection | Description |
---|---|
Set | Set is a collection of elements which can not contain duplicate values. Set is implemented in HashSets, LinkedHashSets, TreeSet etc |
List | List is a ordered collection of elements which can have duplicates. Lists are classified into ArrayList, LinkedList, Vectors |
Queue | FIFO approach, while instantiating Queue interface you can either choose LinkedList or PriorityQueue. |
Deque | Deque(Double Ended Queue) is used to add or remove elements from both the ends of the Queue(both head and tail) |
Map | Map contains key-values pairs which don't have any duplicates. Map is implemented in HashMap, TreeMap etc. |