CODEWITHSUNDEEP
java
hyperion385
hyperion385

Reputation: 168

Java OO main method confusion

So I'm just starting to learn java and have come to this example:

class Dog {
    int size;
    String breed;
    String name;

    void bark() {
        System.out.println("Ruff! Ruff!");
    }
} // class Dog

class DogTestDrive {

        public static void main(String[] args) {
            Dog d = new Dog();
            d.size = 40;
            d.bark();
        } // end main
} // class DogTestDrive

When I try to run it I get the following error: Error: Main method not found in class Dog, please define the main method as: public static void main(String[] args)

I don't see where is the problem? This should work with only one main mathod.

Upvotes: 1

Views: 214

Answers (5)

carexcer
carexcer

Reputation: 1427

Your code runs right, but make sure that the file is named "DogTestDrive.java", because you must run it. Further, you should declare the class DogTestDrive as public (not necessary).

  class Dog {
        int size;
        String breed;
        String name;

        void bark() {
            System.out.println("Ruff! Ruff!");
        }
    } // class Dog

    public class DogTestDrive {

            public static void main(String[] args) {
                Dog d = new Dog();
                d.size = 40;
                d.bark();
            } // end main
    } // class DogTestDrive

Upvotes: -1

Bohemian
Bohemian

Reputation: 425033

When you start java, you tell it which class to execute. Java finds the main() method in the specified class and calls it.

You need to tell java to execute DogTestDrive.

Note that if you're executing this in an IDE it's as easy as right-clicking on DogTestDrive in your project and chiding "Run".

The class java runs must be a "top level" class - that is one that is declared in its own file of the same name as the class, but with .java added (not a class declared in another class's file).

Upvotes: 3

SimonT
SimonT

Reputation: 2359

In Java, each file with a .java extension has one public class with the same name as the file (e.g. Dog.java has public class Dog {...). A file can have multiple classes, but only one can be public.

When you run a file named Dog.java, Java will try to execute Dog.main in the file. If you want DogTestDrive.main to run then you must put DogTestDrive in DogTestDrive.java As for class Dog {..., can either go in the same file or in its own Dog.java file, the latter being preferred because then classes outside of the file will be able to access it.

Upvotes: 0

Moduo
Moduo

Reputation: 623

What Tim B means is that you have to run DogTestDrive instead of Dog. This way the main method from DogTestDrive is used and no main method in Dog is needed.

Upvotes: 0

Tim B
Tim B

Reputation: 41188

Your main method is in the class DogTestDrive not the class Dog.

Upvotes: 1

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