First java program, does not print anything

Question

I think I wrote the code correctly, but it does not print anything. Can anyone explain me why ?

public class Dogs {

    String name = "";
    String color = "";
    String breed = "";
    boolean hungry = true;

    void changeBarking (boolean True) {
        hungry = True;
    }

    void changeName (String newValue) {
        name = newValue;
    }

    void changeBreed (String newValue) {
        breed = newValue;
    }

    void changeColor (String newValue) {
        color = newValue;
    }

    void printStates() {
        System.out.println("name:" + name);
        System.out.println("color:" + color);
        System.out.println("breed:" + breed);
        System.out.println("hungry:" + hungry);
    }

}

class DogsDemo {
    public static void main(String[] args) {

        Dogs dog1 = new Dogs();
        Dogs dog2 = new Dogs();

        dog1.changeName("Dogas");
        dog1.changeColor("Juodas");
        dog1.changeBarking(true);

        dog2.changeName("Taksas");
        dog2.changeColor("Rudas");
        dog2.changeBarking(false);
    }
}

I dont know why nobody is mentioning it, but wouldnt it be better to a) delete the printStates() method and move the print commands to the main method by calling dog1.variableName or b) overriding the toString method of the dog class...? Just a design hint anyway.. — Ben
– Ben, Commented Dec 28, 2013 at 16:23
Overriding toString() would be better IMO, but accessing the variable directly like dog1.variableName kinda goes against OO encapsulation principles. Those members should be private with setters/getters. — takendarkk
– takendarkk, Commented Dec 28, 2013 at 17:07

Jeroen Vannevel · Accepted Answer · 2013-12-28 16:05:30Z

9

You have to actually call the method that does the printing.

Add

dog1.printStates();
dog2.printStates();

This seems a little awkward as well:

void changeBarking (boolean True) {
     hungry = True;
}

Variable names should start with a lowercase, and calling a boolean variable True is bound to cause confusion. Instead use something like this:

void changeBarking (boolean isBarking) {
     hungry = isBarking;
}

answered Dec 28, 2013 at 16:05

Jeroen Vannevel

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Comments

Tom Leese · Accepted Answer · 2013-12-28 16:05:36Z

3

you are not calling method printStates().

edited Dec 28, 2013 at 16:05

Tom Leese

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answered Dec 28, 2013 at 16:05

sachin garg

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Comments

takendarkk · Accepted Answer · 2013-12-28 16:05:54Z

3

Try adding the lines

dog1.printStates();
dog2.printStates();

in your main() method after you set all your values. Currently you never actually make a call to your printing method.

answered Dec 28, 2013 at 16:05

takendarkk

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Comments

Quentin S. · Accepted Answer · 2013-12-28 16:06:04Z

1

System.out.println(""); allows you to print String. It's what you're doing in the printStates() method, but since you're not calling it at any time, it is not executed.

answered Dec 28, 2013 at 16:06

Quentin S.

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Comments

Rakesh KR · Accepted Answer · 2013-12-28 16:05:37Z

0

Because You are not calling the methd printStates()

Call the method as

dog1.printStates();
dog2.printStates();

answered Dec 28, 2013 at 16:05

Rakesh KR

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Comments

Sitansu · Accepted Answer · 2013-12-28 16:37:29Z

0

The static before the main method, this declares the method as a class method, which means it needs no instance to be called. So as you are going to call a non static method, Java complains because you are trying to call a so called "instance method", which, of course needs an instance first.

Just call dog1.printStates(); and dog2.printStates();inside main method .

class DogsDemo {
    public static void main(String[] args) {
       //  code here
        dog1.printStates();
        dog2.printStates();
    }
}

See this simple program:http://www.daniweb.com/software-development/java/threads/366637/calling-methods-from-main-method

edited Dec 28, 2013 at 16:37

answered Dec 28, 2013 at 16:07

Sitansu

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