Compile from class

[Steve Ni]

If I compile execute file from Class but not Java file, then, what's java.*
package GCJ adapted?
For example, I compile HelloWorld.java by "javac HelloWorld.java" under Sun
JDK1.3, after got HelloWorld.class, I run "gcj --main=HelloWorld -o Hello
HelloWorld.class", does libgcj also be required? When I execute "Hello",
which java..* API's action will be token? Sun JDK API or those in libgcj
java.* API ?