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Commons Collections example source code file (TestReverseListIterator.java)

This example Commons Collections source code file (TestReverseListIterator.java) is included in the DevDaily.com "Java Source Code Warehouse" project. The intent of this project is to help you "Learn Java by Example" TM.

Java - Commons Collections tags/keywords

arraylist, four, four, listiterator, listiterator, nosuchelementexception, nosuchelementexception, one, reverselistiterator, string, testreverselistiterator, three, three, two, util

The Commons Collections TestReverseListIterator.java source code

/*
 *  Licensed to the Apache Software Foundation (ASF) under one or more
 *  contributor license agreements.  See the NOTICE file distributed with
 *  this work for additional information regarding copyright ownership.
 *  The ASF licenses this file to You under the Apache License, Version 2.0
 *  (the "License"); you may not use this file except in compliance with
 *  the License.  You may obtain a copy of the License at
 *
 *      http://www.apache.org/licenses/LICENSE-2.0
 *
 *  Unless required by applicable law or agreed to in writing, software
 *  distributed under the License is distributed on an "AS IS" BASIS,
 *  WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
 *  See the License for the specific language governing permissions and
 *  limitations under the License.
 */
package org.apache.commons.collections.iterators;

import java.util.ArrayList;
import java.util.Arrays;
import java.util.List;
import java.util.ListIterator;
import java.util.NoSuchElementException;

import junit.framework.Test;
import junit.framework.TestSuite;
import junit.textui.TestRunner;

import org.apache.commons.collections.ResettableListIterator;

/**
 * Tests the ReverseListIterator.
 *
 * @version $Revision: $ $Date: 2008-04-10 13:48:07 +0100 (Thu, 10 Apr 2008) $
 */
public class TestReverseListIterator extends AbstractTestListIterator {

    protected String[] testArray = { "One", "Two", "Three", "Four" };

    public static void main(String args[]) {
        String[] testCaseName = { TestReverseListIterator.class.getName() };
        TestRunner.main(testCaseName);
    }

    public static Test suite() {
        return new TestSuite(TestReverseListIterator.class);
    }

    public TestReverseListIterator(String testName) {
        super(testName);
    }

    public ListIterator makeEmptyListIterator() {
        List list = new ArrayList();
        return new ReverseListIterator(list);
    }

    public ListIterator makeFullListIterator() {
        List list = new ArrayList(Arrays.asList(testArray));
        return new ReverseListIterator(list);
    }

    // overrides
    //-----------------------------------------------------------------------
    public void testEmptyListIteratorIsIndeedEmpty() {
        ListIterator it = makeEmptyListIterator();
        
        assertEquals(false, it.hasNext());
        assertEquals(-1, it.nextIndex());  // reversed index
        assertEquals(false, it.hasPrevious());
        assertEquals(0, it.previousIndex());  // reversed index
        
        // next() should throw a NoSuchElementException
        try {
            it.next();
            fail("NoSuchElementException must be thrown from empty ListIterator");
        } catch (NoSuchElementException e) {
        }
        
        // previous() should throw a NoSuchElementException
        try {
            it.previous();
            fail("NoSuchElementException must be thrown from empty ListIterator");
        } catch (NoSuchElementException e) {
        }
    }

    public void testWalkForwardAndBack() {
        ArrayList list = new ArrayList();
        ListIterator it = makeFullListIterator();
        while (it.hasNext()) {
            list.add(it.next());
        }
        
        // check state at end
        assertEquals(false, it.hasNext());
        assertEquals(true, it.hasPrevious());
        
        // this had to be commented out, as there is a bug in the JDK before JDK1.5
        // where calling previous at the start of an iterator would push the cursor
        // back to an invalid negative value
//        try {
//            it.next();
//            fail("NoSuchElementException must be thrown from next at end of ListIterator");
//        } catch (NoSuchElementException e) {
//        }
        
        // loop back through comparing
        for (int i = list.size() - 1; i >= 0; i--) {
            assertEquals("" + i, list.size() - i - 2, it.nextIndex());  // reversed index
            assertEquals(list.size() - i - 1, it.previousIndex());  // reversed index
            
            Object obj = list.get(i);
            assertEquals(obj, it.previous());
        }
        
        // check state at start
        assertEquals(true, it.hasNext());
        assertEquals(false, it.hasPrevious());
        try {
            it.previous();
            fail("NoSuchElementException must be thrown from previous at start of ListIterator");
        } catch (NoSuchElementException e) {
        }
    }

    //-----------------------------------------------------------------------
    public void testReverse() {
        ListIterator it = makeFullListIterator();
        assertEquals(true, it.hasNext());
        assertEquals(3, it.nextIndex());
        assertEquals(false, it.hasPrevious());
        assertEquals(4, it.previousIndex());
        assertEquals("Four", it.next());
        assertEquals(2, it.nextIndex());
        assertEquals(true, it.hasNext());
        assertEquals(3, it.previousIndex());
        assertEquals(true, it.hasPrevious());
        assertEquals("Three", it.next());
        assertEquals(true, it.hasNext());
        assertEquals(1, it.nextIndex());
        assertEquals(true, it.hasPrevious());
        assertEquals(2, it.previousIndex());
        assertEquals("Two", it.next());
        assertEquals(true, it.hasNext());
        assertEquals(0, it.nextIndex());
        assertEquals(true, it.hasPrevious());
        assertEquals(1, it.previousIndex());
        assertEquals("One", it.next());
        assertEquals(false, it.hasNext());
        assertEquals(-1, it.nextIndex());
        assertEquals(true, it.hasPrevious());
        assertEquals(0, it.previousIndex());
        assertEquals("One", it.previous());
        assertEquals("Two", it.previous());
        assertEquals("Three", it.previous());
        assertEquals("Four", it.previous());
    }

    public void testReset() {
        ResettableListIterator it = (ResettableListIterator) makeFullListIterator();
        assertEquals("Four", it.next());
        it.reset();
        assertEquals("Four", it.next());
        it.next();
        it.next();
        it.reset();
        assertEquals("Four", it.next());
    }

}

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