Execute the Main Method Multiple Times in Java

In this tutorial, we will see how one can execute the main() method multiple times in Java.

Approach: Using Static Block

We know that the static block is executed first. Therefore, it can be used to execute the main method explicitly. One is executed implicitly as the main method is automatically invoked by the JVM. Observe the following program.

FileName: ExecuteMainMethodStaticBlock.java

public class ExecuteMainMethodStaticBlock
{
// a static block
static
{
System.out.println("Inside the static block."); // print statement
// calling the main method from the static method
main( new String[] {"For the main method."}); 
}


// main method
public static void main(String[] args)
{
System.out.println("Inside the main method."); // print statement
}
}

Output:

Inside the static block.
Inside the main method
Inside the main method

Explanation: A static block is executed first, and in that block, the main() method is invoked explicitly. Again, JVM executes the main() method implicitly since the main() method serves as the entry of the program.

Approach: Using Recursion

It is a known fact that a method calls itself in recursion. Therefore, recursion can be applied to invoke the main method multiple times. An illustration of it is given below.

FileName: ExecuteMainMethodRecursion.java

public class ExecuteMainMethodRecursion
{
// main method
public static void main(String[] args)
{
// print statement
System.out.println("Inside the main method.");
main( new String[] {"For the main method."}); // recursively calling the main method
}
}

Output:

Inside the main method.
Inside the main method.
Inside the main method.
Inside the main method.
Inside the main method.
?
?
?

Explanation: We have managed to execute the main() method multiple times using recursion. However, this program will not terminate as there is no terminating condition.

In order to terminate the program, we have to write a terminating condition. One can do that with the help of a static variable. Observe the following.

FileName: ExecuteMainMethodRecursion.java

public class ExecuteMainMethodRecursion
{
static int i = 0; // static variable
// main method
public static void main(String[] args)
{
// terminating condition.
if(i >= 5) { return; }
i = i + 1; 
System.out.println("Inside the main method."); // print statement
main( new String[] {"For the main method."}); // recursively calling the main method
}
}

Output:

Inside the main method.
Inside the main method.
Inside the main method.
Inside the main method.
Inside the main method.

Explanation: We have to use a static variable because the main() method is decorated with the static keyword. We want the recursion to occur only five times, and according to that, we have written the terminating condition.

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