Commons Collections example source code file (TestComparatorChain.java)

This example Commons Collections source code file (TestComparatorChain.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

columncomparator, columncomparator, comparablecomparator, comparator, comparatorchain, comparatorchain, comparison, integer, integer, io, linkedlist, list, object, pseudorow, pseudorow, util

The Commons Collections TestComparatorChain.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.comparators;

import java.io.Serializable;
import java.util.Comparator;
import java.util.LinkedList;
import java.util.List;

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

/**
 * Tests for ComparatorChain.
 * 
 * @version $Revision: 646780 $ $Date: 2008-04-10 13:48:07 +0100 (Thu, 10 Apr 2008) $
 * 
 * @author Unknown
 */
public class TestComparatorChain extends AbstractTestComparator {

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

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

    public Comparator makeComparator() {
        ComparatorChain chain = new ComparatorChain(new ColumnComparator(0));
        chain.addComparator(new ColumnComparator(1),true); // reverse the second column
        chain.addComparator(new ColumnComparator(2),false);
        return chain;
    }

    public void testNoopComparatorChain() {
        ComparatorChain chain = new ComparatorChain();
        Integer i1 = new Integer(4);
        Integer i2 = new Integer(6);
        chain.addComparator(new ComparableComparator());

        int correctValue = i1.compareTo(i2);
        assertTrue("Comparison returns the right order",chain.compare(i1,i2) == correctValue);
    }

    public void testBadNoopComparatorChain() {
        ComparatorChain chain = new ComparatorChain();
        Integer i1 = new Integer(4);
        Integer i2 = new Integer(6);
        try {
            chain.compare(i1,i2);
            fail("An exception should be thrown when a chain contains zero comparators.");
        } catch (UnsupportedOperationException e) {

        }
    }

    public void testListComparatorChain() {
        List list = new LinkedList();
        list.add(new ComparableComparator());
        ComparatorChain chain = new ComparatorChain(list);
        Integer i1 = new Integer(4);
        Integer i2 = new Integer(6);

        int correctValue = i1.compareTo(i2);
        assertTrue("Comparison returns the right order",chain.compare(i1,i2) == correctValue);
    }

    public void testBadListComparatorChain() {
        List list = new LinkedList();
        ComparatorChain chain = new ComparatorChain(list);
        Integer i1 = new Integer(4);
        Integer i2 = new Integer(6);
        try {
            chain.compare(i1,i2);
            fail("An exception should be thrown when a chain contains zero comparators.");
        } catch (UnsupportedOperationException e) {

        }
    }


    public void testComparatorChainOnMinvaluedCompatator() {
        // -1 * Integer.MIN_VALUE is less than 0,
        // test that ComparatorChain handles this edge case correctly
        ComparatorChain chain = new ComparatorChain();
        chain.addComparator(
            new Comparator() {
                public int compare(Object a, Object b) {
                    int result = ((Comparable)a).compareTo(b);
                    if(result < 0) {
                        return Integer.MIN_VALUE;
                    } else if(result > 0) {
                        return Integer.MAX_VALUE;
                    } else {
                        return 0;
                    }
                }
            }, true);

        assertTrue(chain.compare(new Integer(4), new Integer(5)) > 0);            
        assertTrue(chain.compare(new Integer(5), new Integer(4)) < 0);            
        assertTrue(chain.compare(new Integer(4), new Integer(4)) == 0);            
    }

    public List getComparableObjectsOrdered() {
        List list = new LinkedList();
        // this is the correct order assuming a
        // "0th forward, 1st reverse, 2nd forward" sort
        list.add(new PseudoRow(1,2,3));
        list.add(new PseudoRow(2,3,5));
        list.add(new PseudoRow(2,2,4));
        list.add(new PseudoRow(2,2,8));
        list.add(new PseudoRow(3,1,0));
        list.add(new PseudoRow(4,4,4));
        list.add(new PseudoRow(4,4,7));
        return list;
    }

    public static class PseudoRow implements Serializable {

        public int cols[] = new int[3];

        public PseudoRow(int col1, int col2, int col3) {
            cols[0] = col1;
            cols[1] = col2;
            cols[2] = col3;
        }

        public int getColumn(int colIndex) {
            return cols[colIndex];
        }

        public String toString() {
            StringBuffer buf = new StringBuffer();
            buf.append("[");
            buf.append(cols[0]);
            buf.append(",");
            buf.append(cols[1]);
            buf.append(",");
            buf.append(cols[2]);
            buf.append("]");
            return buf.toString();
        }

        public boolean equals(Object o) {
            if (!(o instanceof PseudoRow)) {
                return false;
            }

            PseudoRow row = (PseudoRow) o;
            if (getColumn(0) != row.getColumn(0)) {
                return false;
            }

            if (getColumn(1) != row.getColumn(1)) {
                return false;
            }            
            
            if (getColumn(2) != row.getColumn(2)) {
                return false;
            }

            return true;
        }

    }

    public static class ColumnComparator implements Comparator,Serializable {

        protected int colIndex = 0;

        public ColumnComparator(int colIndex) {
            this.colIndex = colIndex;
        }

        public int compare(Object o1, Object o2) {

            int col1 = ( (PseudoRow) o1).getColumn(colIndex);
            int col2 = ( (PseudoRow) o2).getColumn(colIndex);

            if (col1 > col2) {
                return 1;
            } else if (col1 < col2) {
                return -1;
            }

            return 0;
        }
        
        public int hashCode() {
            return colIndex;
        }
        
        public boolean equals(Object that) {
            if(that instanceof ColumnComparator) {
                return colIndex == ((ColumnComparator)that).colIndex;
            } else {
                return false;
            }
        }
        
        private static final long serialVersionUID = -2284880866328872105L;
    }
}