KezvhLib/src-lib/net/kezvh/collections/AbstractIterator.java

   1 package net.kezvh.collections;
   2
   3 import java.util.Iterator;
   4 import java.util.NoSuchElementException;
   5
   6 /**
   7  * @author afflux
   8  * @param <T> type to iterate over
   9  */
  10 public abstract class AbstractIterator<T> implements Iterator<T> {
  11         private T nextObject;
  12         private boolean firstTime = true;
  13         private boolean noMoreElements = false;
  14
  15         /**
  16          * @return the next object
  17          * @throws NoSuchElementException if there are no more elements
  18          */
  19         protected abstract T findNext() throws NoSuchElementException;
  20
  21         private T tryFindNext() {
  22                 this.firstTime = false;
  23                 try {
  24                         return this.findNext();
  25                 } catch (final NoSuchElementException e) {
  26                         this.noMoreElements = true;
  27                         return null;
  28                 }
  29         }
  30
  31         /**
  32          * @see java.util.Iterator#hasNext()
  33          * @return x
  34          */
  35         public final boolean hasNext() {
  36                 if (this.firstTime)
  37                         this.nextObject = this.tryFindNext();
  38                 return !this.noMoreElements;
  39         }
  40
  41         /**
  42          * @see java.util.Iterator#next()
  43          * @return x
  44          */
  45         public final T next() {
  46                 if (this.firstTime)
  47                         this.nextObject = this.tryFindNext();
  48                 if (!this.hasNext())
  49                         throw new NoSuchElementException();
  50                 try {
  51                         return this.nextObject;
  52                 } finally {
  53                         this.nextObject = this.tryFindNext();
  54                 }
  55         }
  56
  57         /**
  58          * By default, throws UnsupportedOperationException. This can be overridden.
  59          *
  60          * @see java.util.Iterator#remove()
  61          */
  62         public void remove() {
  63                 throw new UnsupportedOperationException();
  64         }
  65 }