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Groups > comp.lang.java.programmer > #36822

no easy way to do a reverse pointer?

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public class A {
  private B fld;
  public void setFld(B value) {
    fld = value;
  }
}

So field fld is an object, which means it's a pointer to an instance of type B, and I can have multiple instances of A referencing a single instance of B.
So the easiest way for an instance of B to tell you which instances of A hold a reference?

public class A {
  private B fld;
  public void setFld(B value) {
    if (fld != null) {
      fld.dropRef(this);
    }
    value.refer(this);
    fld = value;
  }
}
public class B {
  private HashSet<A> refs = new HashSet();
  public void refer(A value) {
    refs.add(value);
  }
  public HashSet getRefs() {
    return refs;
  }
  public void dropRef(A value) {
    refs.remove(value);
  }
}

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no easy way to do a reverse pointer? Eric Douglas <e.d.programmer@gmail.com> - 2017-07-07 11:56 -0700
  Re: no easy way to do a reverse pointer? Martin Gregorie <martin@address-in-sig.invalid> - 2017-07-07 19:48 +0000
    Re: no easy way to do a reverse pointer? Eric Douglas <e.d.programmer@gmail.com> - 2017-07-07 13:28 -0700
      Re: no easy way to do a reverse pointer? Martin Gregorie <martin@address-in-sig.invalid> - 2017-07-07 21:47 +0000
      Re: no easy way to do a reverse pointer? Eric Sosman <esosman@comcast-dot-net.invalid> - 2017-07-07 18:06 -0400
        Re: no easy way to do a reverse pointer? lewbloch@gmail.com - 2017-07-14 14:32 -0700

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