main method in Java is starting point of any standalone core Java
application. JVM starts executing Java program from main method and the thread
which executes main is called main thread in Java. Main
method is also an important topics in Java interviews for 2 to 3 years
experienced developer. In this Java article we will couple of questions related
to main method in Java. Apart from Why
main is static in Java, I see following questions keep coming related to
main method :
Can we overload main method in Java ? Which main method JVM will call ?
Can we override main method in Java ?
Can we make main final in Java?
Can we make main synchronized in Java ?
How to call a non static method from main in Java ?
Can we
overload main in Java ?
Yes you can overload
main method in Java, nothing wrong with this but Java will only call your
specific main method, i.e. main method with following signature :
public static void main(String[] args) or public
static void main(String args...) which is main method as variable
argument method and only supported post Java 5 world.
Can we
override main in Java ?
No you can not overrdie main method in Java, Why? because main is static
method and in Java static method is bonded during compile time and you can
not override
static method in Java. If you decalre method with same name and signature its
called method hiding.
Can we
make main final in Java?
Ofcourse you can make main method final in Java. JVM has no issue with
that. Unlike any final
method you can not override main in Java.
Can we
make main synchronized in Java?
Yes, main can be synchronized in Java, synchronized
modifier is allowed in main signature and you can make your main method
synchronized in Java.
How to
call a non static method from main in Java ?
This question applies not only to main but all static methods in Java.
Since non
static methods can not be called from static context directly, you need to
first create an Object as local variable and then you can call non static method
using that object, as shown in following example :
import java.util.Date;
/**
* Java program to show how to call non static method from static method
in Java
*
* @author http://java67.blogspot.com
*/
public class
StaticTest {
public static void
main(String args[]) {
// calling non
static method from main in Java
//printCurrentTime();
//compile time error - can not call non static method from main
StaticTest test = new
StaticTest();
test.printCurrentTime();
}
public void printCurrentTime(){
System.out.println(new Date());
}
}
Output:
Tue Nov 06 19:07:54
IST 2012
So these were some of the frequently asked questions about main method in
Java. This are not only help to answer interview question but also to build
your concept on main method in Java.
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