How does Java APIs become available for use ?

[jignesh soni]

JDK1.6 is installed on computer.
When I create a new Java class, I can import a package as "import java.io.*;"
How does compiler find this java.io.* ? If I want a custom class to be available for use, then I need to set the path for that class in classpath variable. For java.io.*, there is no classpath set. I checked Path variable and its set for java.exe file. So how and where is the path for these APIs set ?

Thanks

[Bear Bibeault]

They are included with the Java installation, and the compiler knows where they are.

[Campbell Ritchie]

They line inside a file called rt.jar (I think) and the compiler is programmed to look there.

[jignesh soni]

They are included with the Java installation, and the compiler knows where they are.

I understand that they are included with java installation, but how do compiler finds these classes ? How is classpath set for these packages ? Can I see them in environment variables ? If not, then how is classpath set ?

They line inside a file called rt.jar (I think) and the compiler is programmed to look there

So, is rt.jar set in some classpath ? When compiler starts looking for some classes it will look in environment variables. So is this rt.jar set in any environment variable ? If compiler does not find classpath in environment variables, does it look for anywhere else ? If no, then how is rt.jar set to be made available to compiler ?

Thanks

[Ulf Dittmer]

It's not part of the classpath, the compiler simply knows where it should be in a JRE installation, like Bear and Campbell said. Try removing the file and see what happens :-)

[Stuart A. Burkett]

jignesh soni wrote:I understand that they are included with java installation, but how do compiler finds these classes ?

How classes are found

[jignesh soni]

Thanks for the link.

I was reading that link.

Note that the classes which implement the Java 2 SDK tools are in a separate archive from the bootstrap classes

what is meant by Java 2 SDK tools ? Is tools something different from classes ?
Please give some examples of SDK tools. I may be using it, but I am not aware they are called SDK tools

In general, you only have to specify the location of user classes. Bootstrap classes and extension classes are found "automatically".

What about core java classes. It does not say anything about core java classes and packages. Are core java classes known as extension classes ? If not, then how are these classes found ?

Thanks

[Stuart A. Burkett]

jignesh soni wrote:

In general, you only have to specify the location of user classes. Bootstrap classes and extension classes are found "automatically".

What about core java classes. It does not say anything about core java classes and packages. Are core java classes known as extension classes ? If not, then how are these classes found ?

As you have already been told, the core Java classes are in rt.jar

Bootstrap classes - Classes that comprise the Java platform, including the classes in rt.jar and several other important jar files.

[Stuart A. Burkett]

jignesh soni wrote:what is meant by Java 2 SDK tools ? Is tools something different from classes ?
Please give some examples of SDK tools.

JDK Tools and Utilities