Commons Collections example source code file (TestLRUMap.java)

This example Commons Collections source code file (TestLRUMap.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, hashmap, integer, integer, lru, lrucounter, lrucounter, lrumap, lrumap, map, object, object, string, testlrumap, util

The Commons Collections TestLRUMap.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;

import java.util.ArrayList;
import java.util.HashMap;
import java.util.Iterator;
import java.util.Map;
import java.util.Set;

import junit.framework.Test;

/**
 * Tests LRUMap.
 * 
 * @version $Revision: 646780 $ $Date: 2008-04-10 13:48:07 +0100 (Thu, 10 Apr 2008) $
 * 
 * @author James Strachan
 * @author Morgan Delagrange
 * @author Stephen Colebourne
 */
public class TestLRUMap extends TestSequencedHashMap {
    
    public TestLRUMap(String testName) {
        super(testName);
    }

    public static Test suite() {
        return BulkTest.makeSuite(TestLRUMap.class);
    }

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

    //-----------------------------------------------------------------------
    public Map makeEmptyMap() {
        LRUMap map = new LRUMap();
        return map;
    }

    /**
     * Override as test uses iterator() and getKey() in combination which doesn't work.
     */
    public String[] ignoredTests() {
        return new String[] {"TestLRUMap.bulkTestMapEntrySet.testMapEntrySetIteratorEntry"};
    }

    //-----------------------------------------------------------------------
    public void testRemoveLRU() {
        LRUMap map2 = new LRUMap(3);
        map2.put(new Integer(1),"foo");
        map2.put(new Integer(2),"foo");
        map2.put(new Integer(3),"foo");
        map2.put(new Integer(4),"foo"); // removes 1 since max size exceeded
        map2.removeLRU();  // should be Integer(2)

        assertTrue("Second to last value should exist",map2.get(new Integer(3)).equals("foo"));
        assertTrue("First value inserted should not exist", map2.get(new Integer(1)) == null);
    }

    public void testMultiplePuts() {
        LRUMap map2 = new LRUMap(2);
        map2.put(new Integer(1),"foo");
        map2.put(new Integer(2),"bar");
        map2.put(new Integer(3),"foo");
        map2.put(new Integer(4),"bar");

        assertTrue("last value should exist",map2.get(new Integer(4)).equals("bar"));
        assertTrue("LRU should not exist", map2.get(new Integer(1)) == null);
    }

    /**
     * Confirm that putAll(Map) does not cause the LRUMap
     * to exceed its maxiumum size.
     */
    public void testPutAll() {
        LRUMap map2 = new LRUMap(3);
        map2.put(new Integer(1),"foo");
        map2.put(new Integer(2),"foo");
        map2.put(new Integer(3),"foo");

        HashMap hashMap = new HashMap();
        hashMap.put(new Integer(4),"foo");

        map2.putAll(hashMap);

        assertTrue("max size is 3, but actual size is " + map2.size(),
                   map2.size() == 3);
        assertTrue("map should contain the Integer(4) object",
                   map2.containsKey(new Integer(4)));
    }

    /**
     * Test that the size of the map is reduced immediately
     * when setMaximumSize(int) is called
     */
    public void testSetMaximumSize() {
        LRUMap map = new LRUMap(6);
        map.put("1","1");
        map.put("2","2");
        map.put("3","3");
        map.put("4","4");
        map.put("5","5");
        map.put("6","6");
        map.setMaximumSize(3);

        assertTrue("map should have size = 3, but actually = " + map.size(), 
                   map.size() == 3);
    }

    public void testGetPromotion() {
        LRUMap map = new LRUMap(3);
        map.put("1","1");
        map.put("2","2");
        map.put("3","3");
        // LRU is now 1 (then 2 then 3)

        // promote 1 to top
        // eviction order is now 2,3,1
        map.get("1");
        
        // add another value, forcing a remove
        // 2 should be evicted (then 3,1,4)
        map.put("4","4");
        
        Iterator keyIterator = map.keySet().iterator();
        Object[] keys = new Object[3];
        for (int i = 0; keyIterator.hasNext() ; ++i) {
            keys[i] = keyIterator.next();
        }

        assertTrue("first evicted should be 3, was " + keys[0], keys[0].equals("3"));
        assertTrue("second evicted should be 1, was " + keys[1], keys[1].equals("1"));
        assertTrue("third evicted should be 4, was " + keys[2], keys[2].equals("4"));
        
    }

    /**
     * You should be able to subclass LRUMap and perform a 
     * custom action when items are removed automatically
     * by the LRU algorithm (the removeLRU() method).
     */
    public void testLRUSubclass() {
        LRUCounter counter = new LRUCounter(3);
        // oldest <--> newest
        // 1
        counter.put("1","foo");
        // 1 2
        counter.put("2","foo");
        // 1 2 3
        counter.put("3","foo");
        // 2 3 1
        counter.put("1","foo");
        // 3 1 4 (2 goes out)
        counter.put("4","foo");
        // 1 4 5 (3 goes out)
        counter.put("5","foo");
        // 4 5 2 (1 goes out)
        counter.put("2","foo");
        // 4 2
        counter.remove("5");

        assertTrue("size should be 2, but was " + counter.size(), counter.size() == 2);
        assertTrue("removedCount should be 3 but was " + counter.removedCount,
                   counter.removedCount == 3);

        assertTrue("first removed was '2'",counter.list.get(0).equals("2"));
        assertTrue("second removed was '3'",counter.list.get(1).equals("3"));
        assertTrue("third removed was '1'",counter.list.get(2).equals("1"));

        assertTrue("oldest key is '4'",counter.get(0).equals("4"));
        assertTrue("newest key is '2'",counter.get(1).equals("2"));
    }


    protected void entrySetEqualsMap(Set set, Map m) {
        // Overridden because LRUMap.get(Object) actually alters the map,
        // so there's no way to verify that the entry set and map contain
        // the same entries
    }

    private class LRUCounter extends LRUMap {
        int removedCount = 0;
        ArrayList list = new ArrayList(3); 

        LRUCounter(int i) {
            super(i);
        }

        protected void processRemovedLRU(Object key, Object value) {
            ++removedCount;
            list.add(key);
        }
    }

}