First Program in Java:
package myapp1;
public class MyApp1 {
public static void main(String[] args) {
System.out.println("Welcome
to Java ");
to Java ");
}
}
package myapp1; it
is a package
is a package
public class MyApp1:
Ø
public is access modifier
keyword
public is access modifier
keyword
Ø
class is keyword used to
define a class.
class is keyword used to
define a class.
Ø
MyApp1 is the name of
class.
MyApp1 is the name of
class.
public static void main(String[] args) { Your statements goes here }
Ø
public: is access modifier keyword
public: is access modifier keyword
Ø
static: static is
keyword which is used to call any member of class without an object.
static: static is
keyword which is used to call any member of class without an object.
Ø Void: no return type
Ø Main(): main is the method, which is the starting point
of program, every java program must have main method, it is the entry point
from which java program starts execution.
of program, every java program must have main method, it is the entry point
from which java program starts execution.
Ø String[] : string array : it indicates main can string
array arguments , args is the name of array.
array arguments , args is the name of array.
Ø {}: Delimiters, creates the block of main
println(): this is an output
method it produces output result , println() method is the member of printstream
class, and we use this method with the out object in System class.
method it produces output result , println() method is the member of printstream
class, and we use this method with the out object in System class.
Package: The collection of classes is called Package , it is the
container of classes.
container of classes.
Examples: java.lang, java.util,java.awt,
java.io,java.applet,java.net,java.math,java.text,java.security, javax.swing,
java.io,java.applet,java.net,java.math,java.text,java.security, javax.swing,
How to import/include a package?
Import statement is used to import any package.
import java.lang.Byte;
import java.lang.Boolean;
import java.util.Arrays;
import
java.util.Date;
java.util.Date;
import java.lang.*;
import java.util.*;
Note: java.lang
is default packages, and we don’t need to import it for using its
classes and methods.
is default packages, and we don’t need to import it for using its
classes and methods.
Class: It is blue print
for creating objects.
for creating objects.
How to create our custom class:
We use class keyword for
creating our own custom classes.
creating our own custom classes.
class A
{
Your code goes here
}
How to create custom method in class A:
public static void hello()
{
System.out.println("Hello method ");
}
Complete Program:
package myapp1;
import java.lang.*;
import java.util.*;
class A
{
public static void hello()
{
System.out.println("Hello method ");
}
}
public class MyApp1 {
public static void
main(String[] args) {
main(String[] args) {
System.out.println("Welcome to Java ");
A.hello();
}
}
Program#2:
package
javaapplication4;
javaapplication4;
import
java.util.*;
java.util.*;
public class
JavaApplication4 {
JavaApplication4 {
public static void main(String[] args) {
System.out.println(new Date());
}
}
Program#3:
package
javaapplication4;
javaapplication4;
public class
JavaApplication4 {
JavaApplication4 {
public static void main(String[] args) {
System.out.println(10+10);
System.out.println(20-5);
System.out.println(4*3);
System.out.println(12/2);
System.out.println(13%2);
}
}
Program#4:
package
javaapplication4;
javaapplication4;
public class
JavaApplication4 {
JavaApplication4 {
public static void main(String[] args) {
System.out.println("10+10=\t"+(10+10));
System.out.println("20-5=\t"+(20-5));
System.out.println("4*3=\t"+(4*3));
System.out.println("12/2=\t"+(12/2));
System.out.println("13%2=\t"+(13%2));
}
}
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