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    • com.samskivert.util.Comparators Maven / Gradle / Ivy

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    //
// $Id$
//
// samskivert library - useful routines for java programs
// Copyright (C) 2001-2011 Michael Bayne, et al.
//
// This library is free software; you can redistribute it and/or modify it
// under the terms of the GNU Lesser General Public License as published
// by the Free Software Foundation; either version 2.1 of the License, or
// (at your option) any later version.
//
// This library is distributed in the hope that it will be useful,
// but WITHOUT ANY WARRANTY; without even the implied warranty of
// MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU
// Lesser General Public License for more details.
//
// You should have received a copy of the GNU Lesser General Public
// License along with this library; if not, write to the Free Software
// Foundation, Inc., 59 Temple Place, Suite 330, Boston, MA 02111-1307 USA

package com.samskivert.util;

import java.util.Comparator;

import com.samskivert.annotation.ReplacedBy;

/**
 * A repository for standard comparators.
 */
public class Comparators
{
    /**
     * A comparator that compares the toString() value of all objects case insensitively.
     */
    @ReplacedBy("com.google.common.collect.Ordering.from(String.CASE_INSENSITIVE_ORDER).onResultOf(Functions.toStringFunction()).nullsLast()")
    public static final Comparator LEXICAL_CASE_INSENSITIVE = new Comparator() {
        public int compare (Object o1, Object o2)
        {
            if (o1 == o2) { // catches null == null
                return 0;
            } else if (o1 == null) {
                return 1;
            } else if (o2 == null) {
                return -1;
            }
            // now that we've filtered all nulls, compare the toString()s
            return String.CASE_INSENSITIVE_ORDER.compare(o1.toString(), o2.toString());
        }
    };

    /**
     * A comparator that compares {@link Comparable} instances.
     */
    @ReplacedBy("com.google.common.collect.Ordering.natural().nullsLast()")
    public static final Comparator> COMPARABLE =
        new Comparator>() {
        public int compare (Comparable o1, Comparable o2)
        {
            if (o1 == o2) { // catches null == null
                return 0;
            } else if (o1 == null) {
                return 1;
            } else if (o2 == null) {
                return -1;
            }
            return o1.compareTo(o2); // null-free
        }
    };

    /**
     * Returns the Comparator for Comparables, properly cast.
     *
     * 
    This example illustrates the type-safe way to obtain a natural-ordering Comparator:
     * 
         *    Comparator<Integer> = Comparators.comparable();
     * 
    
     */
    // we can't do the "more correct" > here as that causes other
    // code to freak out; I don't entirely understand why
    @ReplacedBy("com.google.common.collect.Ordering.natural().nullsLast()")
    public static final > Comparator comparable ()
    {
        @SuppressWarnings("unchecked") Comparator comp = (Comparator)COMPARABLE;
        return comp;
    }

    /**
     * Compares two bytes, returning 1, 0, or -1.
     * TODO: remove when Java finally has this method in Byte.
     */
    @ReplacedBy("com.google.common.primitives.SignedBytes.compare()")
    public static int compare (byte value1, byte value2)
    {
        return (value1 < value2 ? -1 : (value1 == value2 ? 0 : 1));
    }

    /**
     * Compares two chars, returning 1, 0, or -1.
     * TODO: remove when Java finally has this method in Character.
     */
    @ReplacedBy("com.google.common.primitives.Chars.compare()")
    public static int compare (char value1, char value2)
    {
        return (value1 < value2 ? -1 : (value1 == value2 ? 0 : 1));
    }

    /**
     * Compares two shorts, returning 1, 0, or -1.
     * TODO: remove when Java finally has this method in Character.
     */
    @ReplacedBy("com.google.common.primitives.Shorts.compare()")
    public static int compare (short value1, short value2)
    {
        return (value1 < value2 ? -1 : (value1 == value2 ? 0 : 1));
    }

    /**
     * Compares two integers in an overflow safe manner, returning 1, 0, or -1.
     * TODO: remove when Java finally has this method in Integer.
     */
    @ReplacedBy("com.google.common.primitives.Ints.compare()")
    public static int compare (int value1, int value2)
    {
        return (value1 < value2 ? -1 : (value1 == value2 ? 0 : 1));
    }

    /**
     * Compares two longs in an overflow safe manner, returning 1, 0, or -1.
     * TODO: remove when Java finally has this method in Long.
     */
    @ReplacedBy("com.google.common.primitives.Longs.compare()")
    public static int compare (long value1, long value2)
    {
        return (value1 < value2 ? -1 : (value1 == value2 ? 0 : 1));
    }

    /**
     * Returns the first non-zero value in the supplied list. This is useful for combining
     * comparators:
     * 
         * return Comparators.compare(name.compareTo(oname), Comparators.compare(price, oprice), ...);
     * 
    
     * If all values in the array are zero, zero is returned.
     */
    @ReplacedBy("com.google.common.collect.ComparisonChain")
    public static int combine (int ... values)
    {
        for (int value : values) {
            if (value != 0) {
                return value;
            }
        }
        return 0;
    }

    // Double.compare() exists

    // Float.compare() exists

    /**
     * Compares two booleans, returning 1, 0, or -1.
     * TODO: remove when Java finally has this method in Boolean.
     */
    @ReplacedBy("com.google.common.primitives.Booleans.compare()")
    public static int compare (boolean value1, boolean value2)
    {
        return (value1 == value2) ? 0 : (value1 ? 1 : -1);
    }
}
    
    
    
    

    




    
    
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