Ошибка main method not found

When you use the java command to run a Java application from the command line, e.g.,

java some.AppName arg1 arg2 ...

the command loads the class that you nominated and then looks for the entry point method called main. More specifically, it is looking for a method that is declared as follows:

package some;
public class AppName {
    ...
    public static void main(final String[] args) {
        // body of main method follows
        ...
    }
}

The specific requirements for the entry point method are:

1. The method must be in the nominated class.
2. The name of the method must be «main» with exactly that capitalization¹.
3. The method must be public.
4. The method must be static ².
5. The method’s return type must be void.
6. The method must have exactly one argument and argument’s type must be String[] ³.

(The argument may be declared using varargs syntax; e.g. String... args. See this question for more information. The String[] argument is used to pass the arguments from the command line, and is required even if your application takes no command-line arguments.)

If anyone of the above requirements is not satisfied, the java command will fail with some variant of the message:

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

Or, if you are running an extremely old version of Java:

java.lang.NoSuchMethodError: main
Exception in thread "main"

If you encounter this error, check that you have a main method and that it satisfies all of the six requirements listed above.

^{1 — One really obscure variation of this is when one or more of the characters in «main» is NOT a LATIN-1 character … but a Unicode character that looks like the corresponding LATIN-1 character when displayed.
2 — Here is an explanation of why the method is required to be static.
3 — String must be the standard java.lang.String class and not to a custom class named String that is hiding the standard class.}

Особенности IDE, которыми не следует пользоваться. Теоретически несколько классов в одном файле использовать возможно, и некоторые IDE сразу же позволяют использовать этот функционал. Но не следует делать так: всегда выносите классы в отдельные файлы (если не вложенные, само собой):
У автора в настройках запуска проекта явно указано, где расположен метод main. В NetBeans не работаю (но это именно аргумент, например, -classpath «ваш_путьdelbin» del.BankAccountTest), в Eclipse выставляется так (и файл BankAccountTest.class уже есть в bin — смотрите ниже):

Как воспроизвести:

Изначально два файла, в каждом ко классу:

Компилируем, получаем в bin два файла классов BankAccount.class и BankAccountTest.class, запускаем.

Удаляем BankAccountTest.java, а код переносим в BankAccount.java. Компилируем, запускаем.

А теперь удалите BankAccountTest.class — и IDE не сможет сослаться на main из удаленного BankAccountTest.class, несмотря на то, что, как выше показано, код второго класса перенесли в BankAccount.java (т.е. восстановили «исходное» состояние) — IDE не воспринимает класс BankAccountTest для компиляции.

Добрый день.

Столкнулся с не возможностью запуска в IDE без добавления метода main. Код не компилируется в IDE и не проходит валидации.
Error: Main method not found in class com.javarush.task.pro.task06.task0615.Earth, please define the main method as:
public static void main(String[] args)

Если метод добавить — код компилируется, но валидации по прежнему не проходит.
как правильно эту задачу запустить в IDE?

I’m learning Java for my course and I’ve hit a brick wall. I’ve been tasked with developing a simple command line program. To make things easier I was given the following sample code to modify so I wouldn’t have to start from scratch.

package assignment;

public class Main {
private final static String[] mainMenuOpts = {"Students","Lecturers","Admin","Exit"};
private final static String[] studentMenuOpts = {"Add Student","List all Students","Find a Student","Return to Main Menu"};
private Menu mainMenu = new Menu("MAIN MENU",mainMenuOpts);
private Menu studentMenu = new Menu("STUDENT MENU",studentMenuOpts);
private DataStore data = new DataStore();
private java.io.PrintStream out = System.out;
private ReadKb reader = new ReadKb();
/** Creates a new instance of Main */
public Main() {
    run();
}

private void run(){
    int ret = mainMenu.display();
    while(true){
        switch(ret){
            case 1: students();break;
            case 2: lecturers(); break;
            case 3: admin(); break;
            case 4: exit(); break;
        }
        ret = mainMenu.display();
    }
}
private void students(){
    int ret = studentMenu.display();
    while(ret != 4){
        switch(ret){
            case 1: addStudent();break;
            case 2: listStudents(); break;
            case 3: findStudent(); break;
        }
        ret = studentMenu.display();
    }
}
private void lecturers(){
    out.println("nLecturers not yet implemented");
}
private void admin(){
    out.println("nAdmin not yet implemented");
}
//Student methods
private void addStudent(){
    out.println("ntAdd New Student");
    //prompt for details
    //add student to the datastore
    //ask if they want to enter another student - 
    // if so call addStudent again
    //otherwise the method completes and the studentMenu will display again

}
private void listStudents(){
    out.println("ntStudent Listing");
    //list all students from the datastore
}
private void findStudent(){
    out.println("ntFind Student");
    out.print("Enter Search String: ");
    //reasd search text
    //use datastore method to get list of students that contain the search string
    //display matching students

}
// end Student methods
private void exit() {
    data.save();  //call the datastore method that will save to file
    out.println("nnGoodbye :)");
    System.exit(0);
    }
}

I’m using NetBeans and when I try to run the project I get this error:

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

I just want to get the program running so I can understand the code better. I understand the error, but have no idea where to implement the main method in this wall of text. I’ve been experimenting for hours, but obviously as a newbie I’m completely useless. Any help would be greatly appreciated.