Resolve class name from bytecode

Question

Is it possible to dig up a classes name from bytecode which is formed from the class\' source code?

The situation is this: I get a classes bytecode remotely from so

Answer 1

The easiest way is probably using something like ASM:

import org.objectweb.asm.ClassReader;
import org.objectweb.asm.commons.EmptyVisitor;

public class PrintClassName {
  public static void main(String[] args) throws IOException {
    class ClassNamePrinter extends EmptyVisitor {
      @Override
      public void visit(int version, int access, String name, String signature,
          String superName, String[] interfaces) {
        System.out.println("Class name: " + name);
      }
    }

    InputStream binary = new FileInputStream(args[0]);
    try {
      ClassReader reader = new ClassReader(binary);
      reader.accept(new ClassNamePrinter(), 0);
    } finally {
      binary.close();
    }
  }
}

If you can't use a 3rd party library, you could read the class file format yourself.