Groups | Search | Server Info | Keyboard shortcuts | Login | Register [http] [https] [nntp] [nntps]

Groups > comp.lang.java.programmer > #8583

Re: optional operation

Show all headers | View raw

Thanks, but I am still confused.  How can a buffer not be backed by an
accessible array?

I tried this code, and hasArray returns true.  However, hasArray2
returns false.

			byte[] b = new byte[numfloats*4];
			dis.read(b, 0, numfloats*4);

			ByteBuffer bb = ByteBuffer.wrap(b);
			boolean hasArray = bb.hasArray();
			FloatBuffer fb2 = bb.asFloatBuffer();
			boolean hasArray2 = fb2.hasArray();

I'm trying to get a float[] out of this, but I can't if hasArray2
returns false.







On Oct 5, 12:30 pm, Patricia Shanahan <p...@acm.org> wrote:
> On 10/5/2011 9:49 AM, bob wrote:
>
> > I'm looking at the docs for FloatBuffer, and in many places it says
> > "(optional operation)".  What's the deal with this?  Can we use the
> > operation or not?
>
> The term "optional operation" is used in interface and abstract class
> declarations to indicate a method that the implementation may be allowed
> to throw UnsupportedOperationException.
>
> There are two useful places to look for more information:
>
> 1. The full description of the method. For example, FloatBuffer's array
> method is defined to throw UnsupportedOperationException "If this buffer
> is not backed by an accessible array".
>
> 2. Especially in java.util, there are interfaces with many different
> implementing classes, and you may need to look at the API documentation
> for the implementing class you are using to find out which operations it
> supports.
>
> Patricia

Back to comp.lang.java.programmer | Previous | Next — Previous in thread | Next in thread | Find similar

Thread

optional operation bob <bob@coolgroups.com> - 2011-10-05 09:49 -0700
  Re: optional operation Patricia Shanahan <pats@acm.org> - 2011-10-05 10:30 -0700
    Re: optional operation bob <bob@coolgroups.com> - 2011-10-05 14:20 -0700
      Re: optional operation markspace <-@.> - 2011-10-05 15:51 -0700
        Re: optional operation markspace <-@.> - 2011-10-05 16:05 -0700
          Re: optional operation bob <bob@coolgroups.com> - 2011-10-05 23:46 -0700
            Re: optional operation Lew <lewbloch@gmail.com> - 2011-10-06 06:47 -0700

csiph-web