No main method identified?

Question

Really new to java here. I am trying to build on an abstract class, Animals, extending it to a subclass Ducks. I'll then create an object ducksworth, that proves Duck inherited the methods from the superclass animals, and can call on references to the abstract class variables. When I try and run my code in Netbeans, it is unable to find a main method call, even though the class AllAnimals contains a main call. Any help would be appreciated? This code is entirely written in a single file in Netbeans.

Ideally what I would like as output is "feather"

abstract class Animal {

String FUR= "fur";
String FEATHER = "feather";
String SCALE = "scale";
String SHELL = "shell";
String SKIN = "skin";

abstract String getCovering( );
abstract void makeSound();
abstract boolean canFly( );

}

class Duck extends Animal {
    String covering  = FEATHER;
    String sound = "quack";
    boolean flight = true;
    String getCovering() {
        System.out.println("Ducks are covered in " + covering);
        return covering;
    }
    void makeSound() { 
        System.out.println(sound);
    }
    boolean canFly() { 
        return flight; 
    }
}

class allanimals {
    public static void main(String[] args) {
        Duck ducksworth = new Duck();
        ducksworth.getCovering();
    }
}

Answer 1

As everyone said. Putting actual class below.

Changes done:

1. class name allanimals changed to AllAnimals for better standard.
2. class AllAnimals is made public for jvm to access static main method.
3. File name is given as public class name - AllAnimals.java

File name : AllAnimals.java

abstract class Animal {

String FUR= "fur";
String FEATHER = "feather";
String SCALE = "scale";
String SHELL = "shell";
String SKIN = "skin";

abstract String getCovering( );
abstract void makeSound();
abstract boolean canFly( );

}

class Duck extends Animal {
    String covering  = FEATHER;
    String sound = "quack";
    boolean flight = true;
    String getCovering() {
        System.out.println("Ducks are covered in " + covering);
        return covering;
    }
    void makeSound() { 
        System.out.println(sound);
    }
    boolean canFly() { 
        return flight; 
    }
}

public class AllAnimals {
    public static void main(String[] args) {
        Duck ducksworth = new Duck();
        ducksworth.getCovering();
    }
}

Answer 2

How are you running the project?

It's simplest to have each class in a file so you could simply compile and run the class with your main https://www.protechtraining.com/content/java_fundamentals_tutorial-hello_world

Alternatively, take a look here: Java: Multiple class declarations in one file

https://www.quora.com/Can-we-keep-more-than-one-class-in-a-single-java-file

Answer 3

This is not the JDK 8 idiom I'd recommend. Prefer an interface to an abstract class. Add default methods where appropriate.

When will we see the end of Animal as the go-to inheritance example? Not today, apparently.

Here's how I might do it:

public interface Animal {
    String getCovering();
    void makeSound();
    boolean canFly();
}


public class Duck implements Animal {    
    public String getCovering() { return "feathers"; }
    public void makeSound() { return "quack"; }
    boolean canFly() { return true; } 
}

It's not too soon to learn about JUnit:

public class AnimalTest {

    @Test
    public void testList() {
        // setup
        List<Animal> animals = Collections.singletonList(new Duck());
        List<String> expectedCoverings = Collections.singletonList("feathers");
        List<String> expectedSounds = Collections.singletonList("quack");
        List<Boolean> expectedFly = Collections.singletonList(Boolean.TRUE);
        // exercise
        // assert
        for (int i = 0; i < animals.size(); ++i) {
            Assert.assertEquals(expectedCovering.get(i), animals.get(i).getCovering());
            Assert.assertEquals(expectedSound.get(i), animals.get(i).makeSound());
            Assert.assertEquals(expectedFly.get(i), animals.get(i).canFly());
        }
    }
}

The test is easy to extend as you add more Animal implementations.

Answer 4

At least one class in file should be the public one, in this case is preferable that the file get galled allanimals.java and this class must be marked as the public one.