Question about packages.

[Andrew Stallard]

Whenever I try to use package declarations on classes, even when I put them in a folder with the same name as the package declaration, are unrecognizable to other classes. However, when using the NetBeans IDE I do not have this problem.

For Example:

 package graphics;
public class Circle {
private double radius;
public double getArea(double radius){
return Math.PI*radius*radius;
}
public double getCircumfrence(double radius){
return Math.PI*2*radius;
}
}   

Here is the class CircleTest in the same folder called "graphics:"

 package graphics;
public class CircleTest{
public static void main(String[]args){
Circle quack=new Circle();
for(int i=1;i<8;i++){
System.out.println(quack.getArea(i)+" "+quack.getCircumfrence(i));
}
}
}

   

When attempting to compile, I get these errors, indicating the class Circle can not be found:

CircleTest.java:4: cannot find symbol
symbol : class Circle
location: class graphics.CircleTest
Circle quack=new Circle();
^
CircleTest.java:4: cannot find symbol
symbol : class Circle
location: class graphics.CircleTest
Circle quack=new Circle();
^
2 errors

Nevertheless, it runs just fine in the IDE.

[Christophe Verré]

You need to put the graphics package in the classpath. On the command line, this can be done using "javac -cp . CircleTest.java" in the graphics directory. IDEs are smart enough to find other classes in the same package, not the command line.

[Andrew Stallard]

Christophe Verré wrote:You need to put the graphics package in the classpath. On the command line, this can be done using "javac -cp . CircleTest.java" in the graphics directory. IDEs are smart enough to find other classes in the same package, not the command line.

Unfortunately, that didn't work.

Thanks anyway

[Jesper de Jong]

What Christophe wrote doesn't look correct. You have to put the graphics package in the classpath, as he says. But you don't do that by going into the directory 'graphics' and then specifying '-cp .'.

Instead, go to the parent directory that of the 'graphics' directory, and add that to the classpath. For example:

C:\MyProject\graphics> cd ..

C:\MyProject> javac -cp . graphics\CircleTest.java

C:\MyProject> java -cp . graphics.CircleTest

[Christophe Verré]

What Christophe wrote doesn't look correct.

Sorry, that isn't correct indeed.

[Rahul Kurup]

This is a compilation error rather than a runtime NoClassDefFound error. So I don't think setting CLASSPATH will help.

While compiling from command line remain one level higher from the package structure. Lets say your CircleTest.java file is in D:\java\graphics then navigate to D:\java and execute

javac graphics\*.java

This will compile and place the class files in your graphics folder. If you want the class files in some other folder you can use -d option of javac.

[Andrew Stallard]

Jesper Young wrote:What Christophe wrote doesn't look correct. You have to put the graphics package in the classpath, as he says. But you don't do that by going into the directory 'graphics' and then specifying '-cp .'.

Instead, go to the parent directory that of the 'graphics' directory, and add that to the classpath. For example:

C:\MyProject\graphics> cd ..

C:\MyProject> javac -cp . graphics\CircleTest.java

C:\MyProject> java -cp . graphics.CircleTest

Yes, that worked. Thank You.

However, you need to use the frontslash, at least if you've been liberated from microserfdom.