// file = ch1base/Rock.java
package ch1base;
public class Rock {
  public void whoIsThis() {
    System.out.println( "You're listening to the "+this.getClass().getName()+" band." );
  }
}

// file = ch1band/BlackSabbath.java
package ch1band;
import ch1base.*;
public class BlackSabbath extends Rock {
  public static void main (String[] args) {
     new BlackSabbath().run(); 
  }
  public void run() {
    whoIsThis();
    start();
  }
  private void start() {
    System.out.println("OK, let's go for \"Iron Man\"... Let me see your f*ing hands!");
  }
}

D:\JAVA\java1probe\cert>javac ch1base/Rock.java

D:\JAVA\java1probe\cert>javac ch1band/BlackSabbath.java

D:\JAVA\java1probe\cert>java ch1band/BlackSabbath
You're listening to the ch1band.BlackSabbath band.
OK, let's go for "Iron Man"... Let me see your f*ing hands!

package ch1base;
public class Rock {
  public void whoIsThis() {
    System.out.println( "You're listening to the "+this.getClass().getName()+" band." );
  }
  protected void start() {
    System.out.println( "Preparing to the rock session: tuning the sound..." );
  }
}

D:\JAVA\java1probe\cert>javac ch1band/BlackSabbath.java
ch1band\BlackSabbath.java:11: start() in ch1band.BlackSabbath cannot override start() in ch1base.Rock; attempting to assign w
eaker access privileges; was protected
  private void start() {
               ^
1 error