access modifiers and inheritance

[See Furst]

Ok so I wrote this code below to look at statics, inheritance and access modifiers and once again Java totally has me scratching my head..

We are told that variables without access modifiers default to access from only within the package.. this is why you have protected variables, so that subclasses is other packages can access those variables.

So check this out.. this completely baffles me.

in one file I have the following:

import static java.lang.System.out;

public class StaticInheritance {
	
	static int thing = 3;
	
	public static void main(String g[]) {
		CanIgetThing cigt = new CanIgetThing();
		out.println ("thing: " + cigt.thing);
		cigt.setThing(5);
		out.println("setthing to 5? " + cigt.getThing());
		
	}
}

In another file I have the following.. This is located in the com\thing\mine subfolder and classpath defaults to \.\ (Yep, Windows XP)

package com.thing.mine;
import StaticInheritance;

class CanIgetThing extends StaticInheritance {
	
	public int getThing() {
		return thing;
	}
	public void setThing(int thing) {
		CanIgetThing.thing = thing;	
	}
}

Why can I access thing from a different package, different class when it's static??? Why can I access it from a different package when it's access is package only???

This code compiles, runs and the output is:

thing: 3
setthing to 5? 5

[Gari Jain]

com/thing/mine/CanIgetThing.java:2: '.' expected
import StaticInheritance;
---------------------------^


This error I am getting while trying to compile your code.

[Ankit Garg]

A class in a package, cannot access a class in the default package...

[Anton Brass]

yep, possibly your IDE helped you somehow out. But if you use plain old javac this code won't compile since you cannot accesss classes out of a package that are in the default one.

[See Furst]

Anton Brass wrote:yep, possibly your IDE helped you somehow out. But if you use plain old javac this code won't compile since you cannot accesss classes out of a package that are in the default one.

No and no... but it was a serious gotcha...

There was a an older class file in the classpath from a previous revision...

Once that class file was deleted...

compilation failed.

Thanks for the help.

I thought something was bass ackwards.

[See Furst]

See Furst wrote:

Anton Brass wrote:yep, possibly your IDE helped you somehow out. But if you use plain old javac this code won't compile since you cannot accesss classes out of a package that are in the default one.

No and no... but it was a serious gotcha...

There was a an older class file in the classpath from a previous revision...

Once that class file was deleted...

compilation failed.

Thanks for the help.

I thought something was bass ackwards.

What I wanted to prove was that this code would not compile because the default access modifier was on the package level:

 

import static java.lang.System.out;
import com.thing.mine.CanIgetThing;

public class StaticInheritance extends CanIgetThing {
	
	public int getThing() {
		return thing;
	}
	public void setThing(int thing) {
		StaticInheritance.thing = thing;	
	}
	
	public static void main(String g[]) {
		StaticInheritance si = new StaticInheritance();
		out.println ("thing: " + si.thing);
		si.setThing(5);
		out.println("setthing to 5? " + si.getThing());
		
	}
}
   

and in CanIgetThing.java

   

package com.thing.mine;


public abstract class CanIgetThing  {
	static int thing = 3;
	public abstract int getThing();
	public abstract void setThing(int thing);
}
 

This fails with the expected "thing is not public error"

however it works when thing is protected:

    

package com.thing.mine;


public abstract class CanIgetThing  {
	protected static int thing = 3;
	public abstract int getThing();
	public abstract void setThing(int thing);
}

thing: 3
setthing to 5? 5