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## org.apache.hadoop.metrics2.util
Class TryIterator<T>

    java.lang.Object
      org.apache.hadoop.metrics2.util.TryIterator<T>

Type Parameters:
  `T` - the type of the iterator

All Implemented Interfaces:
  Iterator<T>

    public abstract class TryIterator<T>

extends Object
implements Iterator<T>

A base class for unmodifiable iterators (throws on remove) This class also makes writing filtering iterators easier, where the only way to discover the end of data is by trying to read it. The same applies to writing iterator wrappers around stream read calls. One only needs to implement the tryNext() method and call done() when done.

Constructor Summary
`TryIterator()`

Method Summary
`T` | `current()`
`protected T` | `done()` Implementations of `tryNext()` must call this method when there are no more elements left in the iteration.
`boolean` | `hasNext()`
`T` | `next()`
`void` | `remove()` Guaranteed to throw UnsupportedOperationException
`protected abstract T` | `tryNext()` Return the next element.

Methods inherited from class java.lang.Object
`clone, equals, finalize, getClass, hashCode, notify, notifyAll, toString, wait, wait, wait`

Constructor Detail

### TryIterator

    public TryIterator()

Method Detail

### tryNext

    protected abstract T tryNext()

  Return the next element. Must call `done()` when done, otherwise infinite loop could occur. If this method throws an exception, any further attempts to use the iterator would result in an `IllegalStateException`.

  Returns:
    the next element if there is one or return `done()`

### done

    protected final T done()

  Implementations of `tryNext()` must call this method when there are no more elements left in the iteration.

  Returns:
    null as a convenience to implement `tryNext()`

### hasNext

    public final boolean hasNext()

  Specified by:
    `hasNext` in interface `Iterator<T>`
  Returns:
    true if we have a next element or false otherwise.

### next

    public final T next()

  Specified by:
    `next` in interface `Iterator<T>`
  Returns:
    the next element if we have one.

### current

    public final T current()

  Returns:
    the current element without advancing the iterator

### remove

    public final void remove()

  Guaranteed to throw UnsupportedOperationException

  Specified by:
    `remove` in interface `Iterator<T>`

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Copyright © 2009 The Apache Software Foundation