An Iterator that returns the elements of a specified array, or other iterators etc. : Iterator « Collections « Java Tutorial






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import java.util.Iterator;
import java.util.NoSuchElementException;

/**
 *  An Iterator that returns the elements of a specified array, or other
 *  iterators etc. The collection of objects returned depends on the
 *  constructor used.
 *
 *  Based on similar Enumerator code by boucherb@users
 *
 * @author fred@users
 * @version 1.9.0
 * @since HSQLDB 1.7.2
 */
public class WrapperIterator implements Iterator {

    private static final Object[] emptyelements = new Object[0];
    private Object[]              elements;
    private int                   i;

    // chained iterators
    private boolean  chained;
    private Iterator it1;
    private Iterator it2;

    /** return only not null elements */
    private boolean notNull;

    /**
     * Constructor for an empty iterator. 
     */
    public WrapperIterator() {
        this.elements = emptyelements;
    }

    /**
     * Constructor for all elements of the specified array. 
     *
     * @param elements the array of objects to enumerate
     */
    public WrapperIterator(Object[] elements) {
        this.elements = elements;
    }

    /**
     * Constructor for not-null elements of specified array. 
     *
     * @param elements the array of objects to iterate
     */
    public WrapperIterator(Object[] elements, boolean notNull) {
        this.elements = elements;
        this.notNull  = notNull;
    }

    /**
     * Constructor for a singleton object iterator
     *
     * @param element the single object to iterate
     */
    public WrapperIterator(Object element) {
        this.elements = new Object[]{ element };
    }

    /**
     * Constructor for a chained iterator that returns the elements of the two
     * specified iterators.
     */
    public WrapperIterator(Iterator it1, Iterator it2) {

        this.it1 = it1;
        this.it2 = it2;
        chained  = true;
    }

    /**
     * Tests if this iterator contains more elements. 
     *
     * @return  <code>true</code> if this iterator contains more elements;
     *          <code>false</code> otherwise.
     */
    public boolean hasNext() {

        // for chained iterators
        if (chained) {
            if (it1 == null) {
                if (it2 == null) {
                    return false;
                }

                if (it2.hasNext()) {
                    return true;
                }

                it2 = null;

                return false;
            } else {
                if (it1.hasNext()) {
                    return true;
                }

                it1 = null;

                return hasNext();
            }
        }

        // for other interators
        if (elements == null) {
            return false;
        }

        for (; notNull && i < elements.length && elements[i] == null; i++) {}

        if (i < elements.length) {
            return true;
        } else {

            // release elements for garbage collection
            elements = null;

            return false;
        }
    }

    /**
     * Returns the next element.
     *
     * @return the next element
     * @throws NoSuchElementException if there is no next element
     */
    public Object next() {

        // for chained iterators
        if (chained) {
            if (it1 == null) {
                if (it2 == null) {
                    throw new NoSuchElementException();
                }

                if (it2.hasNext()) {
                    return it2.next();
                }

                it2 = null;

                next();
            } else {
                if (it1.hasNext()) {
                    return it1.next();
                }

                it1 = null;

                next();
            }
        }

        // for other itertors
        if (hasNext()) {
            return elements[i++];
        }

        throw new NoSuchElementException();
    }

    public int nextInt() {
        throw new NoSuchElementException();
    }

    public long nextLong() {
        throw new NoSuchElementException();
    }

    public void remove() {
        throw new NoSuchElementException();
    }

    public void setValue(Object value) {
        throw new NoSuchElementException();
    }
}








9.37.Iterator
9.37.1.Use Iterator to loop through ArrayList
9.37.2.Use Iterator to loop through the HashMap class
9.37.3.Iterate through a Collection using Java Iterator
9.37.4.Traverse through ArrayList in forward direction using Java ListIterator
9.37.5.Traverse through ArrayList in reverse direction using Java ListIterator
9.37.6.Iterate a Collection and remove an item (Exception, wrong version)
9.37.7.Remove an element from Collection using Java Iterator
9.37.8.Iterator from LinkedList
9.37.9.Iterate through elements of Java LinkedList using Iterator
9.37.10.An Iterator that wraps a number of Iterators
9.37.11.Array Iterator
9.37.12.Create singleton Iterator
9.37.13.Cyclic Iteration
9.37.14.Iterator Union of Iterators
9.37.15.Iterator Utils
9.37.16.Iterator class for sparse values in an array.
9.37.17.Iterator class for values contained in an array range.
9.37.18.Sorted Iterator
9.37.19.Treat an Iterator as an Iterable
9.37.20.An Iterator that returns the elements of a specified array, or other iterators etc.
9.37.21.An Iterator wrapper for an Enumeration.
9.37.22.An Iterator wrapper for an Object[], allow us to deal with all array like structures in a consistent manner.
9.37.23.An iterator that breaks text into lines. The result is equal to BufferedReader.readLine().
9.37.24.Gets the child of the specified element having the specified unique name
9.37.25.Implements an java.util.Iterator over any array
9.37.26.Protects an given iterator by preventing calls to remove().
9.37.27.Returns an iterator over the children of the given element with the given tag name
9.37.28.Use an Iterator to cycle through a collection in the forward direction.
9.37.29.This constructs an Iterator over each day in a date range defined by a focus date and range style.