svn commit: r1127272 - /incubator/jena/Jena2/ARQ/trunk/src/org/openjena/atlas/iterator/IteratorSlotted.java

[an...@apache.org]

Author: andy
Date: Tue May 24 20:34:57 2011
New Revision: 1127272

URL: http://svn.apache.org/viewvc?rev=1127272&view=rev
Log:
Common pattern of iterator implementation.

Added:
    incubator/jena/Jena2/ARQ/trunk/src/org/openjena/atlas/iterator/IteratorSlotted.java   (with props)

Added: incubator/jena/Jena2/ARQ/trunk/src/org/openjena/atlas/iterator/IteratorSlotted.java
URL: http://svn.apache.org/viewvc/incubator/jena/Jena2/ARQ/trunk/src/org/openjena/atlas/iterator/IteratorSlotted.java?rev=1127272&view=auto
==============================================================================
--- incubator/jena/Jena2/ARQ/trunk/src/org/openjena/atlas/iterator/IteratorSlotted.java (added)
+++ incubator/jena/Jena2/ARQ/trunk/src/org/openjena/atlas/iterator/IteratorSlotted.java Tue May 24 20:34:57 2011
@@ -0,0 +1,122 @@
+/*
+ * (c) Copyright 2011 Epimorphics Ltd.
+ * All rights reserved.
+ * [See end of file]
+ */
+
+package org.openjena.atlas.iterator;
+
+import java.util.Iterator ;
+import java.util.NoSuchElementException ;
+
+import com.hp.hpl.jena.sparql.util.Utils ;
+
+/** An Iterator with a one slot lookahead. */  
+abstract class IteratorSlotted<T> implements Iterator<T>
+{
+    // Could move in the async abort part of QueryIterator
+    private boolean finished = false ;
+    private T slot = null ; 
+
+    protected IteratorSlotted() { }
+
+    // -------- The contract with the subclasses 
+    
+    /** Implement this, not next() or nextBinding()
+        Returning null is turned into NoSuchElementException 
+        Does not need to call hasNext (can presume it is true) */
+    protected abstract T moveToNext() ;
+    
+    /** Can return true here then null from moveToNext() to indicate end. */ 
+    protected abstract boolean hasMore() ;
+    // altter add a flag to say if null is a legal value.
+    
+    /** Close the iterator. */
+    protected void closeIterator() { }
+   
+    // -------- The contract with the subclasses 
+
+    protected boolean isFinished() { return finished ; }
+
+    /** final - subclasses implement hasNextBinding() */
+    //@Override
+    public final boolean hasNext()
+    {
+        if ( finished )
+            return false ;
+        if ( slot != null )
+            return false ;
+
+        boolean r = hasMore() ;
+        if ( ! r )
+        {
+            close() ;
+            return false ;
+        }
+        
+        slot = moveToNext() ;
+        if ( slot == null )
+        {
+            close() ;
+            return false ;
+        }
+        return true ;
+    }
+    
+    /** final - autoclose and registration relies on it - implement moveToNextBinding() */
+    //@Override
+    public final T next()
+    {
+        if ( ! hasNext() ) throw new NoSuchElementException(Utils.className(this)) ;
+        
+        T obj = slot ;
+        slot = moveToNext() ;
+        return obj ;
+    }
+    
+    public final T peek()
+    {
+        return slot ;
+    }
+    
+    
+    //@Override
+    public final void remove()
+    {
+        throw new UnsupportedOperationException(Utils.className(this)+".remove") ;
+    }
+    
+    public void close()
+    {
+        if ( finished )
+            return ;
+        closeIterator() ;
+        finished = true ;
+    }
+}
+/*
+ * (c) Copyright 2011 Epimorphics Ltd.
+ * All rights reserved.
+ *
+ * Redistribution and use in source and binary forms, with or without
+ * modification, are permitted provided that the following conditions
+ * are met:
+ * 1. Redistributions of source code must retain the above copyright
+ *    notice, this list of conditions and the following disclaimer.
+ * 2. Redistributions in binary form must reproduce the above copyright
+ *    notice, this list of conditions and the following disclaimer in the
+ *    documentation and/or other materials provided with the distribution.
+ * 3. The name of the author may not be used to endorse or promote products
+ *    derived from this software without specific prior written permission.
+ *
+ * THIS SOFTWARE IS PROVIDED BY THE AUTHOR ``AS IS'' AND ANY EXPRESS OR
+ * IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE IMPLIED WARRANTIES
+ * OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE ARE DISCLAIMED.
+ * IN NO EVENT SHALL THE AUTHOR BE LIABLE FOR ANY DIRECT, INDIRECT,
+ * INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT
+ * NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE,
+ * DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY
+ * THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT
+ * (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE OF
+ * THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
+ */
\ No newline at end of file

Propchange: incubator/jena/Jena2/ARQ/trunk/src/org/openjena/atlas/iterator/IteratorSlotted.java
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