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Commons Collections example source code file (TestPriorityBuffer.java)

This example Commons Collections source code file (TestPriorityBuffer.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, buffer, bufferunderflowexception, bufferunderflowexception, collection, integer, integer, io, nosuchelementexception, nosuchelementexception, object, parent, prioritybuffer, prioritybuffer, random, util

The Commons Collections TestPriorityBuffer.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.buffer;

import java.io.IOException;
import java.util.ArrayList;
import java.util.Arrays;
import java.util.Collection;
import java.util.Comparator;
import java.util.Iterator;
import java.util.Random;

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

import org.apache.commons.collections.Buffer;
import org.apache.commons.collections.BufferUnderflowException;
import org.apache.commons.collections.ComparatorUtils;
import org.apache.commons.collections.collection.AbstractTestCollection;
import org.apache.commons.collections.comparators.ComparableComparator;
import org.apache.commons.collections.comparators.ReverseComparator;

/**
 * Tests the PriorityBuffer.
 * 
 * @version $Revision: 646780 $ $Date: 2008-04-10 13:48:07 +0100 (Thu, 10 Apr 2008) $
 * 
 * @author Michael A. Smith
 * @author Steve Phelps
 */
public class TestPriorityBuffer extends AbstractTestCollection {

    public static void main(String[] args) {
        junit.textui.TestRunner.run(suite());
    }

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

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

    //-----------------------------------------------------------------------  
    public void verify() {
        super.verify();
        PriorityBuffer heap = (PriorityBuffer) collection;

        Comparator c = heap.comparator;
        if (c == null) {
            c = ComparatorUtils.naturalComparator();
        }
        if (!heap.ascendingOrder) {
            c = ComparatorUtils.reversedComparator(c);
        }

        Object[] tree = heap.elements;
        for (int i = 1; i <= heap.size; i++) {
            Object parent = tree[i];
            if (i * 2 <= heap.size) {
                assertTrue("Parent is less than or equal to its left child", c.compare(parent, tree[i * 2]) <= 0);
            }
            if (i * 2 + 1 < heap.size) {
                assertTrue("Parent is less than or equal to its right child", c.compare(parent, tree[i * 2 + 1]) <= 0);
            }
        }
    }

    //-----------------------------------------------------------------------  
    /**
     * Overridden because BinaryBuffer isn't fail fast.
     * @return false
     */
    public boolean isFailFastSupported() {
        return false;
    }

    //-----------------------------------------------------------------------  
    public Collection makeConfirmedCollection() {
        return new ArrayList();
    }

    public Collection makeConfirmedFullCollection() {
        ArrayList list = new ArrayList();
        list.addAll(Arrays.asList(getFullElements()));
        return list;
    }

    /**
     * Return a new, empty {@link Object} to used for testing.
     */
    public Collection makeCollection() {
        return new PriorityBuffer();
    }

    //-----------------------------------------------------------------------  
    public Object[] getFullElements() {
        return getFullNonNullStringElements();
    }

    public Object[] getOtherElements() {
        return getOtherNonNullStringElements();
    }

    //-----------------------------------------------------------------------  
    public void testBufferEmpty() {
        resetEmpty();
        Buffer buffer = (Buffer) collection;

        assertEquals(0, buffer.size());
        assertEquals(true, buffer.isEmpty());
        try {
            buffer.get();
            fail();
        } catch (BufferUnderflowException ex) {}

        try {
            buffer.remove();
            fail();
        } catch (BufferUnderflowException ex) {}
    }
    
    public void testBasicOps() {
        PriorityBuffer heap = new PriorityBuffer();

        heap.add("a");
        heap.add("c");
        heap.add("e");
        heap.add("b");
        heap.add("d");
        heap.add("n");
        heap.add("m");
        heap.add("l");
        heap.add("k");
        heap.add("j");
        heap.add("i");
        heap.add("h");
        heap.add("g");
        heap.add("f");

        assertTrue("heap should not be empty after adds", !heap.isEmpty());

        for (int i = 0; i < 14; i++) {
            assertEquals(
                "get using default constructor should return minimum value in the binary heap",
                String.valueOf((char) ('a' + i)),
                heap.get());

            assertEquals(
                "remove using default constructor should return minimum value in the binary heap",
                String.valueOf((char) ('a' + i)),
                heap.remove());

            if (i + 1 < 14) {
                assertTrue("heap should not be empty before all elements are removed", !heap.isEmpty());
            } else {
                assertTrue("heap should be empty after all elements are removed", heap.isEmpty());
            }
        }

        try {
            heap.get();
            fail("NoSuchElementException should be thrown if get is called after all elements are removed");
        } catch (BufferUnderflowException ex) {}

        try {
            heap.remove();
            fail("NoSuchElementException should be thrown if remove is called after all elements are removed");
        } catch (BufferUnderflowException ex) {}
    }

    public void testBasicComparatorOps() {
        PriorityBuffer heap = new PriorityBuffer(new ReverseComparator(new ComparableComparator()));

        assertTrue("heap should be empty after create", heap.isEmpty());

        try {
            heap.get();
            fail("NoSuchElementException should be thrown if get is called before any elements are added");
        } catch (BufferUnderflowException ex) {}

        try {
            heap.remove();
            fail("NoSuchElementException should be thrown if remove is called before any elements are added");
        } catch (BufferUnderflowException ex) {}

        heap.add("a");
        heap.add("c");
        heap.add("e");
        heap.add("b");
        heap.add("d");
        heap.add("n");
        heap.add("m");
        heap.add("l");
        heap.add("k");
        heap.add("j");
        heap.add("i");
        heap.add("h");
        heap.add("g");
        heap.add("f");

        assertTrue("heap should not be empty after adds", !heap.isEmpty());

        for (int i = 0; i < 14; i++) {

            // note: since we're using a comparator that reverses items, the
            // "minimum" item is "n", and the "maximum" item is "a".

            assertEquals(
                "get using default constructor should return minimum value in the binary heap",
                String.valueOf((char) ('n' - i)),
                heap.get());

            assertEquals(
                "remove using default constructor should return minimum value in the binary heap",
                String.valueOf((char) ('n' - i)),
                heap.remove());

            if (i + 1 < 14) {
                assertTrue("heap should not be empty before all elements are removed", !heap.isEmpty());
            } else {
                assertTrue("heap should be empty after all elements are removed", heap.isEmpty());
            }
        }

        try {
            heap.get();
            fail("NoSuchElementException should be thrown if get is called after all elements are removed");
        } catch (BufferUnderflowException ex) {}

        try {
            heap.remove();
            fail("NoSuchElementException should be thrown if remove is called after all elements are removed");
        } catch (BufferUnderflowException ex) {}
    }

    /**
     * Illustrates bad internal heap state reported in Bugzilla PR #235818. 
     */  
    public void testAddRemove() {
        resetEmpty();
        PriorityBuffer heap = (PriorityBuffer) collection;
        heap.add(new Integer(0));
        heap.add(new Integer(2));
        heap.add(new Integer(4));
        heap.add(new Integer(3));
        heap.add(new Integer(8));
        heap.add(new Integer(10));
        heap.add(new Integer(12));
        heap.add(new Integer(3));
        confirmed.addAll(heap);
        // System.out.println(heap);
        Object obj = new Integer(10);
        heap.remove(obj);
        confirmed.remove(obj);
        // System.out.println(heap);
        verify();
    }
    
    /**
     * Generate heaps staring with Integers from 0 - heapSize - 1.
     * Then perform random add / remove operations, checking
     * heap order after modifications. Alternates minHeaps, maxHeaps.
     *
     * Based on code provided by Steve Phelps in PR #25818
     *
     */
    public void testRandom() {
        int iterations = 500;
        int heapSize = 100;
        int operations = 20;
        Random randGenerator = new Random();
        PriorityBuffer h = null;
        for(int i=0; i < iterations; i++) {
            if (i < iterations / 2) {          
                h = new PriorityBuffer(true);
            } else {
                h = new PriorityBuffer(false);
            }
            for(int r = 0; r < heapSize; r++) {
                h.add( new Integer( randGenerator.nextInt(heapSize)) );
            }
            for( int r = 0; r < operations; r++ ) {
                h.remove(new Integer(r));
                h.add(new Integer(randGenerator.nextInt(heapSize)));
            }
            checkOrder(h);
        }
    }
     
    /**
     * Pops all elements from the heap and verifies that the elements come off
     * in the correct order.  NOTE: this method empties the heap.
     */
    protected void checkOrder(PriorityBuffer h) {
        Integer lastNum = null;
        Integer num = null;
        while (!h.isEmpty()) {
            num = (Integer) h.remove();
            if (h.ascendingOrder) {
                assertTrue(lastNum == null || num.intValue() >= lastNum.intValue());
            } else { // max heap
                assertTrue(lastNum == null || num.intValue() <= lastNum.intValue());
            }
            lastNum = num;
            num = null;
        }
    }
    
    /**
     * Returns a string showing the contents of the heap formatted as a tree.
     * Makes no attempt at padding levels or handling wrapping. 
     */
    protected String showTree(PriorityBuffer h) {
        int count = 1;
        StringBuffer buffer = new StringBuffer();
        for (int offset = 1; count < h.size() + 1; offset *= 2) {
            for (int i = offset; i < offset * 2; i++) {
                if (i < h.elements.length && h.elements[i] != null) 
                    buffer.append(h.elements[i] + " ");
                count++;
            }
            buffer.append('\n');
        }
        return buffer.toString();
    }

    /**
     * Generates 500 randomly initialized heaps of size 100
     * and tests that after serializing and restoring them to a byte array
     * that the following conditions hold:
     * 
     *  - the size of the restored heap is the same 
     *      as the size of the orignal heap
     *  
     *  - all elements in the original heap are present in the restored heap
     *  
     *  - the heap order of the restored heap is intact as 
     *      verified by checkOrder()
     */
    public void testSerialization() {
        int iterations = 500;
        int heapSize = 100;
        PriorityBuffer h;
        Random randGenerator = new Random();
        for (int i = 0; i < iterations; i++) {
            if (i < iterations / 2) {
                h = new PriorityBuffer(true);
            } else {
                h = new PriorityBuffer(false);
            }
            for (int r = 0; r < heapSize; r++) {
                h.add(new Integer(randGenerator.nextInt(heapSize)));
            }
            assertTrue(h.size() == heapSize);
            PriorityBuffer h1 = serializeAndRestore(h);
            assertTrue(h1.size() == heapSize);
            Iterator hit = h.iterator();
            while (hit.hasNext()) {
                Integer n = (Integer) hit.next();
                assertTrue(h1.contains(n));
            }
            checkOrder(h1);
        }
    }

    public PriorityBuffer serializeAndRestore(PriorityBuffer h) {
        PriorityBuffer h1 = null;
        try {
            byte[] objekt = writeExternalFormToBytes(h);
            h1 = (PriorityBuffer) readExternalFormFromBytes(objekt);
        } catch (IOException e) {
            e.printStackTrace();
            fail(e.toString());
        } catch (ClassNotFoundException e) {
            e.printStackTrace();
            fail(e.toString());
        }
        return h1;
    }

    public String getCompatibilityVersion() {
        return "3.2";
    }

//    public void testCreate() throws Exception {
//        resetEmpty();
//        writeExternalFormToDisk((java.io.Serializable) collection, "C:/commons/collections/data/test/PriorityBuffer.emptyCollection.version3.2.obj");
//        resetFull();
//        writeExternalFormToDisk((java.io.Serializable) collection, "C:/commons/collections/data/test/PriorityBuffer.fullCollection.version3.2.obj");
//    }

}

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