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Commons Collections example source code file (TestFilterIterator.java)

This example Commons Collections source code file (TestFilterIterator.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

abstracttestiterator, arrayiterator, filteriterator, filteriterator, iterator, iterator, list, nosuchelementexception, object, predicate, predicate, string, string, testfilteriterator, util

The Commons Collections TestFilterIterator.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.Collections;
import java.util.Iterator;
import java.util.List;
import java.util.NoSuchElementException;

import junit.framework.Test;
import junit.framework.TestSuite;

import org.apache.commons.collections.Predicate;
import org.apache.commons.collections.functors.NotNullPredicate;
import org.apache.commons.collections.functors.TruePredicate;

/**
 * Test the filter iterator.
 *
 * @version $Revision: 646780 $ $Date: 2008-04-10 13:48:07 +0100 (Thu, 10 Apr 2008) $
 * 
 * @author Jan Sorensen
 * @author Ralph Wagner
 * @author Huw Roberts
 */
public class TestFilterIterator extends AbstractTestIterator {

    /** Creates new TestFilterIterator */
    public TestFilterIterator(String name) {
        super(name);
    }

    private String[] array;
    private List list;
    private FilterIterator iterator;
    /**
     * Set up instance variables required by this test case.
     */
    public void setUp() {
        array = new String[] { "a", "b", "c" };
        initIterator();
    }

    /**
     * Tear down instance variables required by this test case.
     */
    public void tearDown() throws Exception {
        iterator = null;
    }

    /**
     * Return the tests included in this test suite.
     */
    public static Test suite() {
        return (new TestSuite(TestFilterIterator.class));
    }

    /**
     * Returns an full iterator wrapped in a
     * FilterIterator that blocks all the elements
     * 
     * @return "empty" FilterIterator
     */
    public Iterator makeEmptyIterator() {
        return makeBlockAllFilter(new ArrayIterator(array));
    }

    /**
     * Returns an array with elements wrapped in a pass-through
     * FilterIterator
     * 
     * @return 
     */
    public Iterator makeFullIterator() {
        array = new String[] { "a", "b", "c" };
        list = new ArrayList(Arrays.asList(array));
        return makePassThroughFilter(list.iterator());
    }

    public void testRepeatedHasNext() {
        for (int i = 0; i <= array.length; i++) {
            assertTrue(iterator.hasNext());
        }
    }

    public void testRepeatedNext() {
        for (int i = 0; i < array.length; i++)
            iterator.next();
        verifyNoMoreElements();
    }

    public void testReturnValues() {
        verifyElementsInPredicate(new String[0]);
        verifyElementsInPredicate(new String[] { "a" });
        verifyElementsInPredicate(new String[] { "b" });
        verifyElementsInPredicate(new String[] { "c" });
        verifyElementsInPredicate(new String[] { "a", "b" });
        verifyElementsInPredicate(new String[] { "a", "c" });
        verifyElementsInPredicate(new String[] { "b", "c" });
        verifyElementsInPredicate(new String[] { "a", "b", "c" });
    }

    /**
     * Test that when the iterator is changed, the hasNext method returns the
     * correct response for the new iterator.
     */
    public void testSetIterator() {
        Iterator iter1 = Collections.singleton(new Object()).iterator();
        Iterator iter2 = Collections.EMPTY_LIST.iterator();
        
        FilterIterator filterIterator = new FilterIterator(iter1);
        filterIterator.setPredicate(TruePredicate.getInstance());
        // this iterator has elements
        assertEquals(true, filterIterator.hasNext());
        
        // this iterator has no elements
        filterIterator.setIterator(iter2);
        assertEquals(false, filterIterator.hasNext());
    }

    /**
     * Test that when the predicate is changed, the hasNext method returns the
     * correct response for the new predicate.
     */
    public void testSetPredicate() {
        Iterator iter = Collections.singleton(null).iterator();

        FilterIterator filterIterator = new FilterIterator(iter);
        filterIterator.setPredicate(TruePredicate.getInstance());
        // this predicate matches
        assertEquals(true, filterIterator.hasNext());
        
        // this predicate doesn't match
        filterIterator.setPredicate(NotNullPredicate.getInstance());
        assertEquals(false, filterIterator.hasNext());
    }

    private void verifyNoMoreElements() {
        assertTrue(!iterator.hasNext());
        try {
            iterator.next();
            fail("NoSuchElementException expected");
        }
        catch (NoSuchElementException e) {
            // success
        }
    }

    private void verifyElementsInPredicate(final String[] elements) {
        Predicate pred = new Predicate() {
            public boolean evaluate(Object x) {
                for (int i = 0; i < elements.length; i++)
                    if (elements[i].equals(x))
                        return true;
                return false;
            }
        };
        initIterator();
        iterator.setPredicate(pred);
        for (int i = 0; i < elements.length; i++) {
            String s = (String)iterator.next();
            assertEquals(elements[i], s);
            assertTrue(i == elements.length - 1 ? !iterator.hasNext() : iterator.hasNext());
        }
        verifyNoMoreElements();

        // test removal
        initIterator();
        iterator.setPredicate(pred);
        if (iterator.hasNext()) {
            Object last = iterator.next();
            iterator.remove();
            assertTrue("Base of FilterIterator still contains removed element.", !list.contains(last));
        }
    }

    private void initIterator() {
        iterator = (FilterIterator) makeFullIterator();
    }

    /**
     * Returns a FilterIterator that does not filter
     * any of its elements
     * 
     * @param i      the Iterator to "filter"
     * @return "filtered" iterator
     */
    protected FilterIterator makePassThroughFilter(Iterator i) {
        Predicate pred = new Predicate() {
                public boolean evaluate(Object x) { return true; }
        };
        return new FilterIterator(i,pred);
    }

    /**
     * Returns a FilterIterator that blocks
     * all of its elements
     * 
     * @param i      the Iterator to "filter"
     * @return "filtered" iterator
     */
    protected FilterIterator makeBlockAllFilter(Iterator i) {
        Predicate pred = new Predicate() {
                public boolean evaluate(Object x) { return false; }
        };
        return new FilterIterator(i,pred);
    }
}

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