abstractarrayiterator.java

Java数据结构开发包

/*
  Copyright (c) 1999, 2000 Brown University, Providence, RI
  
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  PERFORMANCE OF THIS SOFTWARE.
*/

package jdsl.core.ref;

import java.util.NoSuchElementException;
import jdsl.core.api.*;

 

/**
 * A class abstracting the common parts of ArrayPositionIterator and
 * ArrayLocatorIterator.
 *
 * @author Luca Vismara (lv)
 * @version JDSL 2.1.1 
 */
public abstract class AbstractArrayIterator {

  // protected instance variable(s)

  protected int iCurrentIndex_;
  protected int iLastIndex_;


  // private instance variable(s)

  private Accessor [] accessorArray_;


  // protected constructor(s)

  /**
   * Uses the array to store the elements that this iterator
   * traverses.  The array is NOT copied.
   *
   * @param array The elements that this iterator should traverse.
   */
  protected AbstractArrayIterator (Accessor [] array) {
    accessorArray_ = array;
    iCurrentIndex_ = -1;
    if (array != null) {
      iLastIndex_ = array.length-1;
    }
    else {
      iLastIndex_ = -1;
    }
  }

  
  /**
   * Traverses through the array until the first
   * num elements have been returned. The array is NOT copied.
   */
  protected AbstractArrayIterator (Accessor [] array, int num) throws
  BoundaryViolationException {
    accessorArray_ = array;
    iCurrentIndex_ = -1;
    iLastIndex_ = num-1;
    if (num > array.length)
      throw new BoundaryViolationException
	("The number of elements is greater than the size of the array.");
  }


  // public instance method(s) 
  
  public boolean hasNext () {
    return iCurrentIndex_ < iLastIndex_;
  }

  
  public Object element () throws NoSuchElementException {
    checkBeforeStart();
    return accessorArray_[iCurrentIndex_].element();
  }

  /** 
   * Takes O(1) time
   */
  public Object nextObject() {
    return nextAccessor();
  }

  /** 
   * Takes O(1) time
   */
  public Object object() throws NoSuchElementException {    
    checkBeforeStart();
    return accessorArray_[iCurrentIndex_];
  }

  /** 
   * Takes O(1) time
   */
  public void reset(){
    iCurrentIndex_ = -1;
  }


  // protected instance method(s)

  protected void checkBeforeStart () throws NoSuchElementException {
    if (iCurrentIndex_ < 0) throw new NoSuchElementException
				("iterator is in before-the-first state");
  }


  protected Accessor nextAccessor() {
    if(!hasNext()) {
      throw new NoSuchElementException("End of iterator contents reached");
    }
    return accessorArray_[++iCurrentIndex_];
  }

}