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javajava-package

Whether we import source code or byte code of a class when importing that class in java?

I have started learning packages in java.I learned about the import keyword.Now my doubt is whether it is .class file or a .java file that is being imported while we import any class in java.

Solution

  • Does the compiler use .class or .java files for an import?

    Answer: .class files, possibly compiling .java files.

    This works, even in the following case (when there are no .class files):

    // p/a/A.java
package p.a;
import p.b.B;
public class A {
    public static final A DEFAULT_A = new B();
}

// p/b/B.java
package p.b;
import p.a.A;
public class B extends A {
}

    The reason that this (a cyclic dependency) can be dealt with, is that .class files are comparable with .obj / .o object files: there is symbolic information (class and method names) in the .class files. And just as the object files are linked with a linker to an executable or library, the java class loader resolves everything.