Package org.eclipse.rdf4j.common.iteration

Class DelayedIteration<E,X extends Exception>

java.lang.Object
org.eclipse.rdf4j.common.iteration.AbstractCloseableIteration<E,X>
org.eclipse.rdf4j.common.iteration.DelayedIteration<E,X>
All Implemented Interfaces:
AutoCloseable, CloseableIteration<E,X>, Iteration<E,X>
Direct Known Subclasses:
OrderIterator, QueryEvaluationStep.DelayedEvaluationIteration
public abstract class DelayedIteration<E,X extends Exception> extends AbstractCloseableIteration<E,X>
An iteration that delays the creation of the underlying iteration until it is being accessed. This is mainly useful for situations where iteration creation adds considerable overhead but where the iteration may not actually be used, or where a created iteration consumes scarce resources like JDBC-connections or memory. Subclasses must implement the createIteration method, which is called once when the iteration is first needed.

  • Constructor Details

    • DelayedIteration

      protected DelayedIteration()
      Creates a new DelayedIteration.

  • Method Details

    • createIteration

      protected abstract Iteration<? extends E,? extends X> createIteration() throws X
      Creates the iteration that should be iterated over. This method is called only once, when the iteration is first needed.
      Throws:
      X extends Exception

    • hasNext

      public boolean hasNext() throws X
      Calls the hasNext method of the underlying iteration.
      Returns:
      true if the iteration has more elements.
      Throws:
      X

    • next

      public E next() throws X
      Calls the next method of the underlying iteration.
      Returns:
      the next element in the iteration.
      Throws:
      X extends Exception

    • remove

      public void remove() throws X
      Calls the remove method of the underlying iteration.
      Throws:
      X extends Exception

    • handleClose

      protected void handleClose() throws X
      Closes this iteration as well as the underlying iteration if it has already been created and happens to be a CloseableIteration.
      Overrides:
      handleClose in class AbstractCloseableIteration<E,X extends Exception>
      Throws:
      X