Public Static Void Main Adalah

In Java programs, the point from where the program starts its execution or simply the entry point of Java programs is the main() method. Hence, it is one of the most important methods of Java and having a proper understanding of it is very important.

The Java compiler or JVM looks for the main method when it starts executing a Java program. The signature of the main method needs to be in a specific way for the JVM to recognize that method as its entry point. If we change the signature of the method, the program compiles but does not execute.

The execution of the Java program, the java.exe is called. The Java.exe inturn makes Java Native Interface or JNI calls, and they load the JVM. The java.exe parses the command line, generates a new String array, and invokes the main() method. A daemon thread is attached to the main method, and this thread gets destroyed only when the Java program stops execution.

Java main() Method

Syntax: Most common in defining main() method

Java

              class              GeeksforGeeks {            
                            public              static              void              main(String[] args)            
                            {            
                            System.out.println(              "I am a Geek"              );            
                            }            
              }            

Output explanation: Every word in the public static void main statement has tepi a meaning to the JVM.

1. Public

It is an Access modifier, which specifies from where and who can access the method. Making the main() method public makes it globally available. It is made public so that JVM can invoke it from outside the class as it is not present in the current class.

Java

              class              GeeksforGeeks {            
                            private              static              void              main(String[] args)            
                            {            
                            System.out.println(              "I am a Geek"              );            
                            }            
              }            

Error: Main method not found in class, please define the main method as: public static void main(String[] args) or a JavaFX application class must extend javafx.application.Application

2. Static

It is a keyword that is when associated with a method, making it a class-related method. The main() method is static so that JVM can invoke it without instantiating the class. This also saves the unnecessary wastage of memory which would have been used by the object declared only for calling the main() method by the JVM.

Java

              class              GeeksforGeeks {            
                            public              void              main(String[] args)            
                            {            
                            System.out.println(              "I am a Geek"              );            
                            }            
              }            

Error: Main method is not static in class test, please define the main method as: public static void main(String[] args)

3. Void

It is a keyword and is used to specify that a method doesn't return anything. As the main() method doesn'falak return anything, its return type is void. As soon as the main() method terminates, the java acara terminates too. Hence, it doesn't make any sense to return from the main() method as JVM can'horizon do anything with the return value of it.

Java

              class              GeeksforGeeks {            
                            public              static              int              main(String[] args)            
                            {            
                            System.out.println(              "I am a Geek"              );            
                            return              1              ;            
                            }            
              }            

Error: Main method titinada found in class, please define the main method as: public static void main(String[] args) or a JavaFX application class must extend javafx.application.Application

4. main

It is the name of the Java main method. It is the identifier that the JVM looks for as the starting point of the java program. It's not a keyword.

Java

              class              GeeksforGeeks {            
                            public              static              void              myMain(String[] args)            
                            {            
                            System.out.println(              "I am a Geek"              );            
                            }            
              }            

Error: Main method not found in class, please define the main method as: public static void main(String[] args) or a JavaFX application class must extend javafx.application.Application

5. String[] args

It stores Java command-line arguments and is an array of type java.lang.String class. Here, the name of the String array is args but it is titinada fixed and the user can use any name in place of it.

Java

              class              GeeksforGeeks {            
                            public              static              void              main(String[] args)            
                            {            
                            for              (String elem : args)            
                            System.out.println(elem);            
                            }            
              }            

Output:

1 2 3

Apart from the above-mentioned signature of main, you could use public static void main(String args[]) or public static void main(String… args) to call the main function in Java. The main method is called if its stereotip parameter matches that of an array of Strings.

Can the main method be int? If not, why?

Java

              class              GeeksforGeeks {            
              public              static              int              main(String[] args)            
                            {            
                            System.out.println(              "GeeksforGeeks"              );            
                            }            
              }            

Java does not return int implicitly, even if we declare the return type of main as int. We will get a compile-time error:

prg1.java:6: error: missing return statement     }     ^  1 error

Java

              class              GeeksforGeeks {            
                            public              static              int              main(String[] args) {            
                            System.out.println(              "GeeksforGeeks"              );            
                            return              0              ;            
                            }            
              }            

Now, even if we do return 0 or integer explicitly ourselves, from int main. We get a run time error.

Error: Main method must return a value of type void in class GeeksforGeeks, please   define the main method as:   public static void main(String[] args)

Explanation:

The C and C++ programs which return int from main are processes of Operating System. The int value returned from main in C and C++ is exit code or exit status. The exit code of the C or C++ program illustrates, why the program was terminated. Exit code 0 means successful termination. However, the non-hampa exit status indicates an error.

For Example exit code 1 depicts Miscellaneous errors, such as "divide by zero".

The parent process of any child process keeps waiting for the exit status of the child. And after receiving the exit status of the child, cleans up the child process from the process table and free the resources allocated to it. This is why it becomes mandatory for C and C++ programs(which are processes of OS) to pass their exit status from the main explicitly or implicitly.

However, the Java program runs as a 'main thread' in JVM. The Java acara is not even a process of Operating System directly. There is no direct interaction between the Java programa and Operating System. There is no direct allocation of resources to the Java acara directly, or the Java program does not occupy any place in the process table. Whom should it return an exit status to, then? This is why the main method of Java is designed not to return an int or exit status.

But JVM is a process of an operating system, and JVM can be terminated with a certain exit status. With help of java.lang.Runtime.exit(int status) or System.exit(int gengsi).

Can we execute a java programa without main method?

Yes, we can execute a java acara without a main method by using a static block.

A static block in Java is a group of statements that gets executed only once when the class is loaded into the memory by ClassLoader, It is also known as a static initialization block, and it goes into the stack memory.

class StaticBlock {     static     {         System.out.println(             "This class can be executed without main");         System.exit(0);     } }