HELP WITH getClass() method

J

JavaBot•5/15/24, 11:57 PM

J

JavaBot•5/15/24, 11:57 PM

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TIP: Narrow down your issue to simple and precise questions to maximize the chance that others will reply in here.

Uuserexit Consider this class: ```java public class MyClass {...} ``` what is the differ...

K

Kyo-chan•5/16/24, 12:05 AM

You may call getClass() on any object, including one of which you don't know what's it class

Example:

Object o = getMysteryObject(); // this time it gives a LocalDate... But on another call it gives a BigDecimal. You never know
Class<?> objClass = o.getClass();
System.out.println(objClass); // prints LocalDate fully qualified name

Object o = getMysteryObject(); // this time it gives a LocalDate... But on another call it gives a BigDecimal. You never know
Class<?> objClass = o.getClass();
System.out.println(objClass); // prints LocalDate fully qualified name

Object o = getMysteryObject(); // this time it gives a LocalDate... But on another call it gives a BigDecimal. You never know
Class<?> objClass = o.getClass();
System.out.println(objClass); // prints LocalDate fully qualified name

Object o = getMysteryObject(); // this time it gives a LocalDate... But on another call it gives a BigDecimal. You never know
Class<?> objClass = o.getClass();
System.out.println(objClass); // prints LocalDate fully qualified name

U

userexitOP•5/16/24, 12:06 AM

U

userexitOP•5/16/24, 12:07 AM

then what is this guy here saying

U

userexitOP•5/16/24, 12:07 AM

?

U

userexitOP•5/16/24, 12:07 AM

@Kyo-chan

K

Kyo-chan•5/16/24, 12:08 AM

He's saying "I'm a beginner"

K

Kyo-chan•5/16/24, 12:08 AM

If the class you want is MyClass, use MyClass.class
If the class you want is that of an object you got, use getClass() on that object

U

userexitOP•5/16/24, 12:08 AM

I think he means if you have for example:

public class Shape {...}
public class Rectangle extends Shape {...}

public class Shape {...}
public class Rectangle extends Shape {...}

public class Shape {...}
public class Rectangle extends Shape {...}

public class Shape {...}
public class Rectangle extends Shape {...}

and somewhere in your code you have:

Shape shape = new Rectangle();

and you do shape.getClass(); you get the Rectangle class and if its in another package then you cant find resources anymore in your package

KKyo-chan He's saying "I'm a beginner"

U

userexitOP•5/16/24, 12:09 AM

lamo

Uuserexit I think he means if you have for example: ```java public class Shape {...} publ...

U

userexitOP•5/16/24, 12:09 AM

do you think this is what he means

U

userexitOP•5/16/24, 12:09 AM

?

K

Kyo-chan•5/16/24, 12:10 AM

He doesn't mean much other than how if you use getClass() on an object whose variable type isn't a final class, then the possible results are more than just the one.
...... And yeah, that's the point. It's not an issue.

U

userexitOP•5/16/24, 12:10 AM

ah okay

U

userexitOP•5/16/24, 12:10 AM

and btw

U

userexitOP•5/16/24, 12:11 AM

getClass().getResource() will try to find it in the package of the class

U

userexitOP•5/16/24, 12:11 AM

and getClass().getClassLoader().getResource() will try to find it outside right

U

userexitOP•5/16/24, 12:11 AM

what I dont get is how can you have package based resources

U

userexitOP•5/16/24, 12:11 AM

there is only 1 resource folder in java

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userexitOP•5/16/24, 12:12 AM

for example running this:

public class classInsideTestPackage {
    public void checkPath() {
        URL url = getClass().getClassLoader().getResource("resource.txt");
        System.out.println(url.getPath());
    }

    public static void main(String[] args) {
        new classInsideTestPackage().checkPath();
    }
}

public class classInsideTestPackage {
    public void checkPath() {
        URL url = getClass().getClassLoader().getResource("resource.txt");
        System.out.println(url.getPath());
    }

    public static void main(String[] args) {
        new classInsideTestPackage().checkPath();
    }
}

public class classInsideTestPackage {
    public void checkPath() {
        URL url = getClass().getClassLoader().getResource("resource.txt");
        System.out.println(url.getPath());
    }

    public static void main(String[] args) {
        new classInsideTestPackage().checkPath();
    }
}

public class classInsideTestPackage {
    public void checkPath() {
        URL url = getClass().getClassLoader().getResource("resource.txt");
        System.out.println(url.getPath());
    }

    public static void main(String[] args) {
        new classInsideTestPackage().checkPath();
    }
}

U

userexitOP•5/16/24, 12:12 AM

doesnt throw a null error

U

userexitOP•5/16/24, 12:12 AM

U

userexitOP•5/16/24, 12:12 AM

because it looked for it here

K

Kyo-chan•5/16/24, 12:12 AM

Actually, the resources folder is a Maven thing to better organize project. Natively, Java has no such notion

U

userexitOP•5/16/24, 12:12 AM

outside all packages

Uuserexit for example running this: ```java public class classInsideTestPackage { pub...

U

userexitOP•5/16/24, 12:13 AM

if I delete getClassLoader() I get an error

Uuserexit Click to see attachment

U

userexitOP•5/16/24, 12:13 AM

if I delete getClassLoader() and I put the resource inside the testPackage folder I get no error no more

KKyo-chan Actually, the resources folder is a Maven thing to better organize project. Nati...

U

userexitOP•5/16/24, 12:13 AM

yeah so do you know how I can put resources in a specific package only ?

Uuserexit yeah so do you know how I can put resources in a specific package only ?

K

Kyo-chan•5/16/24, 12:14 AM

Isn't that exactly what you just demonstrated you know how to do?

KKyo-chan Isn't that exactly what you just demonstrated you know how to do?

U

userexitOP•5/16/24, 12:14 AM

yes but only after compilation

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userexitOP•5/16/24, 12:14 AM

because then I get the folder of the package in the target/classes folder

U

userexitOP•5/16/24, 12:15 AM

and I can do wahtever I want with it

U

userexitOP•5/16/24, 12:15 AM

but before compiling

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userexitOP•5/16/24, 12:15 AM

How can I decide a resource will go inside a package folder

K

Kyo-chan•5/16/24, 12:15 AM

Just put the resources in folders named exactly like that inside the resources folder

K

Kyo-chan•5/16/24, 12:16 AM

(Though nobody but the Java base library team does that)

KKyo-chan Just put the resources in folders named exactly like that inside the resources f...

U

userexitOP•5/16/24, 12:16 AM

so inside src/main/resources
I put a folder named testPackage
and inside it it will put all the resources inside the testPackage inside target/classes ?

K

Kyo-chan•5/16/24, 12:16 AM

yup

KKyo-chan (Though nobody but the Java base library team does that)

U

userexitOP•5/16/24, 12:16 AM

why do you say that ?

K

Kyo-chan•5/16/24, 12:17 AM

I often mention various things that are true in this world. Don't mind it

KKyo-chan I often mention various things that are true in this world. Don't mind it

U

userexitOP•5/16/24, 12:17 AM

no but I mean is there any logicla reason for which normal people wouldnt do ut

K

Kyo-chan•5/16/24, 12:18 AM

There doesn't exactly seem to be a point to bother with that. There is a little bit more of a point with Java 9+ modules isolation, but even then you can just name folders rather than actual packages.

KKyo-chan There doesn't exactly seem to be a point to bother with that. There is a little ...

U

userexitOP•5/16/24, 12:19 AM

isnt getting resources an enough point ?

K

Kyo-chan•5/16/24, 12:21 AM

You can get resources without putting them in packages, and with putting them in packages named differently to the ones you put your classes in.
Otherwise Maven would have simplified putting resources in the same packages as classes

KKyo-chan You can get resources without putting them in packages, and with putting them in...

U

userexitOP•5/16/24, 12:22 AM

really how can you get such resources

Uuserexit really how can you get such resources

K

Kyo-chan•5/16/24, 12:22 AM

Again, did you not demonstrate you know how?

U

userexitOP•5/16/24, 12:23 AM

I mean u can have a folder inside resource named: jeff

and then do getClass().getClassLoader().getResource("/jeff");

but do u have naother way ?

@Kyo-chan

K

Kyo-chan•5/16/24, 12:24 AM

I don't remember all the details, but if you include the starting / I don't think you need the classLoader

KKyo-chan I don't remember all the details, but if you include the starting / I don't thin...

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userexitOP•5/16/24, 12:24 AM

why, what does the starting / change lol

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