io.cdap.cdap.api.dataset.lib

Class AbstractCloseableIterator<T>

java.lang.Object

io.cdap.cdap.api.dataset.lib.AbstractCloseableIterator<T>

Type Parameters:

T - Type of elements returned by this iterator

All Implemented Interfaces:

CloseableIterator<T>, AutoCloseable, Iterator<T>

public abstract class AbstractCloseableIterator<T>
extends Object
implements CloseableIterator<T>

An abstract that Iterator helps implement an non-removable CloseableIterator. This class is copied from guava AbstractIterator.

Constructor Summary

Constructors

Modifier	Constructor and Description
protected	AbstractCloseableIterator() Constructor for use by subclasses.

Method Summary

Modifier and Type	Method and Description
protected abstract T	computeNext() Returns the next element.
protected T	endOfData() Implementations of computeNext() must invoke this method when there are no elements left in the iteration.
boolean	hasNext()
T	next()
void	remove()

Methods inherited from class java.lang.Object

clone, equals, finalize, getClass, hashCode, notify, notifyAll, toString, wait, wait, wait

Methods inherited from interface io.cdap.cdap.api.dataset.lib.CloseableIterator

close, empty

Methods inherited from interface java.util.Iterator

forEachRemaining

Constructor Detail

AbstractCloseableIterator

protected AbstractCloseableIterator()

Constructor for use by subclasses.

Method Detail

computeNext

protected abstract T computeNext()

Returns the next element. Note: the implementation must call endOfData() when there are no elements left in the iteration. Failure to do so could result in an infinite loop.

The initial invocation of hasNext() or next() calls this method, as does the first invocation of hasNext or next following each successful call to next. Once the implementation either invokes endOfData or throws an exception, computeNext is guaranteed to never be called again.

If this method throws an exception, it will propagate outward to the hasNext or next invocation that invoked this method. Any further attempts to use the iterator will result in an IllegalStateException.

The implementation of this method may not invoke the hasNext or next methods on this instance; if it does, an IllegalStateException will result.

Returns:

the next element if there was one. If endOfData was called during execution, the return value will be ignored.

Throws:

RuntimeException - if any unrecoverable error happens. This exception will propagate outward to the hasNext(), next(), or peek() invocation that invoked this method. Any further attempts to use the iterator will result in an IllegalStateException.

endOfData

protected final T endOfData()

Implementations of computeNext() must invoke this method when there are no elements left in the iteration.

Returns:

null; a convenience so your computeNext implementation can use the simple statement return endOfData();

hasNext

public final boolean hasNext()

Specified by:

hasNext in interface Iterator<T>

next

public final T next()

Specified by:

next in interface Iterator<T>

remove

public void remove()

Specified by:

remove in interface Iterator<T>