throw an exception on a method call

Question

How do I throw and UnsupportedOperationException on a method? So if I have an Iterable object and I'm trying to disallow the remove method for that object.

In the method below I'm returning an iterable object whose iterator's remove I need to disable by throwing an UnsupportedErrorException. Can I do this within the body of the method or how so?

 public Iterable<String> getInNodes (String destinationNodeName) { if (!hasNode(destinationNodeName)) return emptySetOfString; else { for(String e : nodeMap.get(destinationNodeName).inNodes) { emptySetOfString.add(e); } return emptySetOfString; } }

throw new UnsupportedOperationException() ?

Ruan Mendes
– Ruan Mendes

2012-12-05 03:09:58 +00:00
Commented Dec 5, 2012 at 3:09 — Ruan Mendes
– Ruan Mendes, Commented Dec 5, 2012 at 3:09

tjg184 · Accepted Answer · 2012-12-05 03:09:50Z

5

Try this.

@Override public void remove() { throw new UnsupportedOperationException(); }

answered Dec 5, 2012 at 3:09

tjg184

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Comments

Cory Kendall · Accepted Answer · 2012-12-05 03:21:59Z

I may have misunderstood your question.

If you have a normal Iterable, and you want to convert it to an Iterable that generates iterators on which remove can not be called, you can use this monstrosity made possible by anonymous subclassing:

Iterable<String> iterable = // normal Iterable<String> you already have... Iterable<String> noRemoveIteratorGeneratingIterable = new Iterable<String>() { @Override public Iterator<String> iterator() { return new Iterator<String>() { Iterator<String> internalIterator = iterable.iterator(); @Override public boolean hasNext() { return internalIterator.hasNext(); } @Override public String next() { return internalIterator.next(); } @Override public void remove() { throw new UnsupportedOperationException("Nope!"); } }; } };

sge · Accepted Answer · 2012-12-05 03:12:46Z

In your class you can just @Override the original method

public class myIterable extends Iterable { @Override public void remove() { throw new UnsupportedOperationException(); } }

Then create Objects of this class instead of original Iterable.

Yogendra Singh · Accepted Answer · 2012-12-05 03:13:26Z

You can try throwing the message with appropriate message as well:

public void remove() { throw new UnsupportedOperationException("Remove is unsupported on this object"); }

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