testiteratorutils.java

初级java程序员如果想要更深一步提高自己的实力

    /**
     * Gets an immutable Iterator operating on the elements ["a", "b", "c", "d"].
     */
    private Iterator getImmutableIterator() {
        List list = new ArrayList();
        list.add("a");
        list.add("b");
        list.add("c");
        list.add("d");
        return IteratorUtils.unmodifiableIterator(list.iterator());
    }

    /**
     * Gets an immutable ListIterator operating on the elements ["a", "b", "c", "d"].
     */
    private ListIterator getImmutableListIterator() {
        List list = new ArrayList();
        list.add("a");
        list.add("b");
        list.add("c");
        list.add("d");
        return IteratorUtils.unmodifiableListIterator(list.listIterator());
    }

    //-----------------------------------------------------------------------
    /**
     * Test empty iterator
     */
    public void testEmptyIterator() {
        assertSame(EmptyIterator.INSTANCE, IteratorUtils.EMPTY_ITERATOR);
        assertSame(EmptyIterator.RESETTABLE_INSTANCE, IteratorUtils.EMPTY_ITERATOR);
        assertEquals(true, IteratorUtils.EMPTY_ITERATOR instanceof Iterator);
        assertEquals(true, IteratorUtils.EMPTY_ITERATOR instanceof ResettableIterator);
        assertEquals(false, IteratorUtils.EMPTY_ITERATOR instanceof OrderedIterator);
        assertEquals(false, IteratorUtils.EMPTY_ITERATOR instanceof ListIterator);
        assertEquals(false, IteratorUtils.EMPTY_ITERATOR instanceof MapIterator);
        assertEquals(false, IteratorUtils.EMPTY_ITERATOR.hasNext());
        IteratorUtils.EMPTY_ITERATOR.reset();
        assertSame(IteratorUtils.EMPTY_ITERATOR, IteratorUtils.EMPTY_ITERATOR);
        assertSame(IteratorUtils.EMPTY_ITERATOR, IteratorUtils.emptyIterator());
        try {
            IteratorUtils.EMPTY_ITERATOR.next();
            fail();
        } catch (NoSuchElementException ex) {}
        try {
            IteratorUtils.EMPTY_ITERATOR.remove();
            fail();
        } catch (IllegalStateException ex) {}
    }
    
    //-----------------------------------------------------------------------
    /**
     * Test empty list iterator
     */
    public void testEmptyListIterator() {
        assertSame(EmptyListIterator.INSTANCE, IteratorUtils.EMPTY_LIST_ITERATOR);
        assertSame(EmptyListIterator.RESETTABLE_INSTANCE, IteratorUtils.EMPTY_LIST_ITERATOR);
        assertEquals(true, IteratorUtils.EMPTY_LIST_ITERATOR instanceof Iterator);
        assertEquals(true, IteratorUtils.EMPTY_LIST_ITERATOR instanceof ListIterator);
        assertEquals(true, IteratorUtils.EMPTY_LIST_ITERATOR instanceof ResettableIterator);
        assertEquals(true, IteratorUtils.EMPTY_LIST_ITERATOR instanceof ResettableListIterator);
        assertEquals(false, IteratorUtils.EMPTY_LIST_ITERATOR instanceof MapIterator);
        assertEquals(false, IteratorUtils.EMPTY_LIST_ITERATOR.hasNext());
        assertEquals(0, IteratorUtils.EMPTY_LIST_ITERATOR.nextIndex());
        assertEquals(-1, IteratorUtils.EMPTY_LIST_ITERATOR.previousIndex());
        IteratorUtils.EMPTY_LIST_ITERATOR.reset();
        assertSame(IteratorUtils.EMPTY_LIST_ITERATOR, IteratorUtils.EMPTY_LIST_ITERATOR);
        assertSame(IteratorUtils.EMPTY_LIST_ITERATOR, IteratorUtils.emptyListIterator());
        try {
            IteratorUtils.EMPTY_LIST_ITERATOR.next();
            fail();
        } catch (NoSuchElementException ex) {}
        try {
            IteratorUtils.EMPTY_LIST_ITERATOR.previous();
            fail();
        } catch (NoSuchElementException ex) {}
        try {
            IteratorUtils.EMPTY_LIST_ITERATOR.remove();
            fail();
        } catch (IllegalStateException ex) {}
        try {
            IteratorUtils.EMPTY_LIST_ITERATOR.set(null);
            fail();
        } catch (IllegalStateException ex) {}
        try {
            IteratorUtils.EMPTY_LIST_ITERATOR.add(null);
            fail();
        } catch (UnsupportedOperationException ex) {}
    }
    
    //-----------------------------------------------------------------------
    /**
     * Test empty map iterator
     */
    public void testEmptyMapIterator() {
        assertSame(EmptyMapIterator.INSTANCE, IteratorUtils.EMPTY_MAP_ITERATOR);
        assertEquals(true, IteratorUtils.EMPTY_MAP_ITERATOR instanceof Iterator);
        assertEquals(true, IteratorUtils.EMPTY_MAP_ITERATOR instanceof MapIterator);
        assertEquals(true, IteratorUtils.EMPTY_MAP_ITERATOR instanceof ResettableIterator);
        assertEquals(false, IteratorUtils.EMPTY_MAP_ITERATOR instanceof ListIterator);
        assertEquals(false, IteratorUtils.EMPTY_MAP_ITERATOR instanceof OrderedIterator);
        assertEquals(false, IteratorUtils.EMPTY_MAP_ITERATOR instanceof OrderedMapIterator);
        assertEquals(false, IteratorUtils.EMPTY_MAP_ITERATOR.hasNext());
        ((ResettableIterator) IteratorUtils.EMPTY_MAP_ITERATOR).reset();
        assertSame(IteratorUtils.EMPTY_MAP_ITERATOR, IteratorUtils.EMPTY_MAP_ITERATOR);
        assertSame(IteratorUtils.EMPTY_MAP_ITERATOR, IteratorUtils.emptyMapIterator());
        try {
            IteratorUtils.EMPTY_MAP_ITERATOR.next();
            fail();
        } catch (NoSuchElementException ex) {}
        try {
            IteratorUtils.EMPTY_MAP_ITERATOR.remove();
            fail();
        } catch (IllegalStateException ex) {}
        try {
            IteratorUtils.EMPTY_MAP_ITERATOR.getKey();
            fail();
        } catch (IllegalStateException ex) {}
        try {
            IteratorUtils.EMPTY_MAP_ITERATOR.getValue();
            fail();
        } catch (IllegalStateException ex) {}
        try {
            IteratorUtils.EMPTY_MAP_ITERATOR.setValue(null);
            fail();
        } catch (IllegalStateException ex) {}
    }
    
    //-----------------------------------------------------------------------
    /**
     * Test empty map iterator
     */
    public void testEmptyOrderedIterator() {
        assertSame(EmptyOrderedIterator.INSTANCE, IteratorUtils.EMPTY_ORDERED_ITERATOR);
        assertEquals(true, IteratorUtils.EMPTY_ORDERED_ITERATOR instanceof Iterator);
        assertEquals(true, IteratorUtils.EMPTY_ORDERED_ITERATOR instanceof OrderedIterator);
        assertEquals(true, IteratorUtils.EMPTY_ORDERED_ITERATOR instanceof ResettableIterator);
        assertEquals(false, IteratorUtils.EMPTY_ORDERED_ITERATOR instanceof ListIterator);
        assertEquals(false, IteratorUtils.EMPTY_ORDERED_ITERATOR instanceof MapIterator);
        assertEquals(false, IteratorUtils.EMPTY_ORDERED_ITERATOR.hasNext());
        assertEquals(false, IteratorUtils.EMPTY_ORDERED_ITERATOR.hasPrevious());
        ((ResettableIterator) IteratorUtils.EMPTY_ORDERED_ITERATOR).reset();
        assertSame(IteratorUtils.EMPTY_ORDERED_ITERATOR, IteratorUtils.EMPTY_ORDERED_ITERATOR);
        assertSame(IteratorUtils.EMPTY_ORDERED_ITERATOR, IteratorUtils.emptyOrderedIterator());
        try {
            IteratorUtils.EMPTY_ORDERED_ITERATOR.next();
            fail();
        } catch (NoSuchElementException ex) {}
        try {
            IteratorUtils.EMPTY_ORDERED_ITERATOR.previous();
            fail();
        } catch (NoSuchElementException ex) {}
        try {
            IteratorUtils.EMPTY_ORDERED_ITERATOR.remove();
            fail();
        } catch (IllegalStateException ex) {}
    }
    
    //-----------------------------------------------------------------------
    /**
     * Test empty map iterator
     */
    public void testEmptyOrderedMapIterator() {
        assertSame(EmptyOrderedMapIterator.INSTANCE, IteratorUtils.EMPTY_ORDERED_MAP_ITERATOR);
        assertEquals(true, IteratorUtils.EMPTY_ORDERED_MAP_ITERATOR instanceof Iterator);
        assertEquals(true, IteratorUtils.EMPTY_ORDERED_MAP_ITERATOR instanceof MapIterator);
        assertEquals(true, IteratorUtils.EMPTY_ORDERED_MAP_ITERATOR instanceof OrderedMapIterator);
        assertEquals(true, IteratorUtils.EMPTY_ORDERED_MAP_ITERATOR instanceof ResettableIterator);
        assertEquals(false, IteratorUtils.EMPTY_ORDERED_MAP_ITERATOR instanceof ListIterator);
        assertEquals(false, IteratorUtils.EMPTY_ORDERED_MAP_ITERATOR.hasNext());
        assertEquals(false, IteratorUtils.EMPTY_ORDERED_MAP_ITERATOR.hasPrevious());
        ((ResettableIterator) IteratorUtils.EMPTY_ORDERED_MAP_ITERATOR).reset();
        assertSame(IteratorUtils.EMPTY_ORDERED_MAP_ITERATOR, IteratorUtils.EMPTY_ORDERED_MAP_ITERATOR);
        assertSame(IteratorUtils.EMPTY_ORDERED_MAP_ITERATOR, IteratorUtils.emptyOrderedMapIterator());
        try {
            IteratorUtils.EMPTY_ORDERED_MAP_ITERATOR.next();
            fail();
        } catch (NoSuchElementException ex) {}
        try {
            IteratorUtils.EMPTY_ORDERED_MAP_ITERATOR.previous();
            fail();
        } catch (NoSuchElementException ex) {}
        try {
            IteratorUtils.EMPTY_ORDERED_MAP_ITERATOR.remove();
            fail();
        } catch (IllegalStateException ex) {}
        try {
            IteratorUtils.EMPTY_ORDERED_MAP_ITERATOR.getKey();
            fail();
        } catch (IllegalStateException ex) {}
        try {
            IteratorUtils.EMPTY_ORDERED_MAP_ITERATOR.getValue();
            fail();
        } catch (IllegalStateException ex) {}
        try {
            IteratorUtils.EMPTY_ORDERED_MAP_ITERATOR.setValue(null);
            fail();
        } catch (IllegalStateException ex) {}
    }
    
    //-----------------------------------------------------------------------
	/**
	 * Test next() and hasNext() for an immutable Iterator.
	 */
    public void testUnmodifiableIteratorIteration() {
        Iterator iterator = getImmutableIterator();

        assertTrue(iterator.hasNext());

        assertEquals("a", iterator.next());

        assertTrue(iterator.hasNext());

        assertEquals("b", iterator.next());

        assertTrue(iterator.hasNext());

        assertEquals("c", iterator.next());

        assertTrue(iterator.hasNext());

        assertEquals("d", iterator.next());

        assertTrue(!iterator.hasNext());
    }

    /**
     * Test next(), hasNext(), previous() and hasPrevious() for an immutable
     * ListIterator.
     */
    public void testUnmodifiableListIteratorIteration() {
        ListIterator listIterator = getImmutableListIterator();

        assertTrue(!listIterator.hasPrevious());
        assertTrue(listIterator.hasNext());

        assertEquals("a", listIterator.next());

        assertTrue(listIterator.hasPrevious());
        assertTrue(listIterator.hasNext());

        assertEquals("b", listIterator.next());

        assertTrue(listIterator.hasPrevious());
        assertTrue(listIterator.hasNext());

        assertEquals("c", listIterator.next());

        assertTrue(listIterator.hasPrevious());
        assertTrue(listIterator.hasNext());

        assertEquals("d", listIterator.next());

        assertTrue(listIterator.hasPrevious());
        assertTrue(!listIterator.hasNext());

        assertEquals("d", listIterator.previous());

        assertTrue(listIterator.hasPrevious());
        assertTrue(listIterator.hasNext());

        assertEquals("c", listIterator.previous());

        assertTrue(listIterator.hasPrevious());
        assertTrue(listIterator.hasNext());

        assertEquals("b", listIterator.previous());

        assertTrue(listIterator.hasPrevious());
        assertTrue(listIterator.hasNext());

        assertEquals("a", listIterator.previous());

        assertTrue(!listIterator.hasPrevious());
        assertTrue(listIterator.hasNext());
    }

    /**
     * Test remove() for an immutable Iterator.
     */
    public void testUnmodifiableIteratorImmutability() {
        Iterator iterator = getImmutableIterator();

        try {
            iterator.remove();
            // We shouldn't get to here.
            fail("remove() should throw an UnsupportedOperationException");
        } catch (UnsupportedOperationException e) {
            // This is correct; ignore the exception.
        }

        iterator.next();

        try {
            iterator.remove();
            // We shouldn't get to here.
            fail("remove() should throw an UnsupportedOperationException");
        } catch (UnsupportedOperationException e) {
            // This is correct; ignore the exception.
        }

    }

    /**
     * Test remove() for an immutable ListIterator.
     */
    public void testUnmodifiableListIteratorImmutability() {
    	ListIterator listIterator = getImmutableListIterator();

        try {
            listIterator.remove();
            // We shouldn't get to here.
            fail("remove() should throw an UnsupportedOperationException");
        } catch (UnsupportedOperationException e) {
            // This is correct; ignore the exception.
        }

        try {
            listIterator.set("a");
            // We shouldn't get to here.
            fail("set(Object) should throw an UnsupportedOperationException");
        } catch (UnsupportedOperationException e) {
            // This is correct; ignore the exception.
        }

        try {
            listIterator.add("a");
            // We shouldn't get to here.
            fail("add(Object) should throw an UnsupportedOperationException");
        } catch (UnsupportedOperationException e) {
            // This is correct; ignore the exception.
        }

        listIterator.next();

        try {
            listIterator.remove();
            // We shouldn't get to here.
            fail("remove() should throw an UnsupportedOperationException");
        } catch (UnsupportedOperationException e) {
            // This is correct; ignore the exception.
        }

        try {
            listIterator.set("a");
            // We shouldn't get to here.
            fail("set(Object) should throw an UnsupportedOperationException");
        } catch (UnsupportedOperationException e) {
            // This is correct; ignore the exception.
        }

        try {
            listIterator.add("a");
            // We shouldn't get to here.
            fail("add(Object) should throw an UnsupportedOperationException");
        } catch (UnsupportedOperationException e) {
            // This is correct; ignore the exception.
        }
    }
}