I have several classes (lock and key). I am trying to branch on the
outcome of boolean value of isOpen. But I keep on getting null exception
error when I try to conditional test the isOpen status.  What is wrong;

Any information is greatly appreciated!
a newbee!

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public class lock{

  public Lock (int combination){
    ...
  }

  public boolean isOpen() {
     return open:
  }

public boolean open;
}
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public class key{

  public Key (int combination){
    ....
  }

  public void getIfOpen(){
   if (lock.isOpen(true))
     ....
   }
}
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