testcomparator.java

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/*
 * Copyright 1999-2004 The Apache Software Foundation
 *
 * Licensed 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.comparators;

import java.io.IOException;
import java.io.FileNotFoundException;
import java.io.Serializable;
import java.util.Collections;
import java.util.Comparator;
import java.util.LinkedList;
import java.util.List;

import org.apache.commons.collections.TestObject;

public abstract class TestComparator extends TestObject {

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

    public abstract Comparator makeComparator();
    public abstract List getComparableObjectsOrdered();

    public Object makeObject() {
        return makeComparator();
    }

    /**
     * There were no Comparators in version 1.x.
     * 
     * @return 2
     */
    public int getCompatibilityVersion() {
        return 2;
    }

    public void reverseObjects(List list) {
        Collections.reverse(list);
    }

    public void randomizeObjects(List list) {
        Collections.shuffle(list);
    }

    /**
     * Sort object according to the given Comparator.
     * 
     * @param list       List to sort
     * @param comparator sorting comparator
     */
    public void sortObjects(List list, Comparator comparator) {

        Collections.sort(list,comparator);

    }

    public boolean supportsEmptyCollections() {
        return false;
    }

    public boolean supportsFullCollections() {
        return false;
    }

    public void testEmptyListSort() {
        List list = new LinkedList();
        sortObjects(list,makeComparator());

        List list2 = new LinkedList();
        
        assertTrue("Comparator cannot sort empty lists",
                   list2.equals(list));
    }

    public void testReverseListSort() {
        Comparator comparator = makeComparator();

        List randomList = getComparableObjectsOrdered();
        reverseObjects(randomList);
        sortObjects(randomList,comparator);

        List orderedList = getComparableObjectsOrdered();

        assertTrue("Comparator did not reorder the List correctly",
                   orderedList.equals(randomList));

    }

    public void testRandomListSort() {
        Comparator comparator = makeComparator();

        List randomList = getComparableObjectsOrdered();
        randomizeObjects(randomList);
        sortObjects(randomList,comparator);

        List orderedList = getComparableObjectsOrdered();

        /* debug 
        Iterator i = randomList.iterator();
        while (i.hasNext()) {
            System.out.println(i.next());
        }
        */

        assertTrue("Comparator did not reorder the List correctly",
                   orderedList.equals(randomList));

    }

    /**
     * Nearly all Comparators should be Serializable.
     */
    public void testComparatorIsSerializable() {
        Comparator comparator = makeComparator();
        assertTrue("This comparator should be Serializable.",
                   comparator instanceof Serializable);
    }

    public String getCanonicalComparatorName(Object object) {
        StringBuffer retval = new StringBuffer();
        retval.append("data/test/");
        String colName = object.getClass().getName();
        colName = colName.substring(colName.lastIndexOf(".")+1,colName.length());
        retval.append(colName);
        retval.append(".version");
        retval.append(getCompatibilityVersion());
        retval.append(".obj");
        return retval.toString();
    }

    /**
     * Compare the current serialized form of the Comparator
     * against the canonical version in CVS.
     */
    public void testComparatorCompatibility() throws IOException, ClassNotFoundException {
        Comparator comparator = null;

        // test to make sure the canonical form has been preserved
	try {
	    comparator = 
		(Comparator) readExternalFormFromDisk
		(getCanonicalComparatorName(makeComparator()));
	} catch (FileNotFoundException exception) {

	    boolean autoCreateSerialized = false;

	    if(autoCreateSerialized) {
		comparator = makeComparator();
		String fileName = getCanonicalComparatorName(comparator);
		writeExternalFormToDisk((Serializable) comparator, fileName);
		fail("Serialized form could not be found.  A serialized version " +
		     "has now been written (and should be added to CVS): " + fileName);
	    } else {
		fail("The Serialized form could be located to test serialization " +
		     "compatibility: " + exception.getMessage());
	    }
	}

        
        // make sure the canonical form produces the ordering we currently
        // expect
        List randomList = getComparableObjectsOrdered();
        reverseObjects(randomList);
        sortObjects(randomList,comparator);

        List orderedList = getComparableObjectsOrdered();

        assertTrue("Comparator did not reorder the List correctly",
                   orderedList.equals(randomList));
    }

}