linux-x86/sample/lambda/DefaultMethods/ArrayIterator.java

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

/**
 * The code sample illustrates the usage of default methods in the JDK 8. Most
 * implementations of {@link Iterator} don't provide a useful
 * {@link Iterator#remove()} method, however,
 * they still have to implement this method to throw
 * an UnsupportedOperationException. With the default method, the same
 * default behavior in interface Iterator itself can be provided.
 */
public class ArrayIterator {

    /** Close the constructor because ArrayIterator is part of the utility
     * class.
     */
    protected ArrayIterator() {
        throw new UnsupportedOperationException();
    }

    /**
     * Returns an iterator that goes over the elements in the array.
     *
     * @param <E> type of an array element
     * @param array source array to iterate over it
     * @return an iterator that goes over the elements in the array
     */
    public static <E> Iterator<E> iterator(final E[] array) {
        return new Iterator<E>() {
            /**
             * Index of the current position
             *
             */
            private int index = 0;

            /**
             * Returns the next element in the iteration
             *
             * @return the next element in the iteration
             * @throws NoSuchElementException if the iteration has no more
             * elements
             */
            @Override
            public boolean hasNext() {
                return (index < array.length);
            }

            /**
             * Returns {@code true} if the iteration has more elements. (In
             * other words, returns {@code true} if {@link #next} returns
             * an element, rather than throwing an exception.)
             *
             * @return {@code true} if the iteration has more elements
             */
            @Override
            public E next() {
                if (!hasNext()) {
                    throw new NoSuchElementException();
                }
                return array[index++];
            }

            /**
             * This method does not need to be overwritten in JDK 8.
             */
            //@Override
            //public void remove() {
            //    throw UnsupportedOperationException(
            //            "Arrays don't support remove.")
            //}
        };
    }

    /**
     * Sample usage of the ArrayIterator
     *
     * @param args command-line arguments
     */
    public static void main(final String[] args) {
        Iterator<String> it = ArrayIterator.iterator(
                new String[]{"one", "two", "three"});

        while (it.hasNext()) {
            System.out.println(it.next());
        }
    }
}