    001    /*
    002     * Copyright (C) 2010 The Guava Authors
    003     *
    004     * Licensed under the Apache License, Version 2.0 (the "License");
    005     * you may not use this file except in compliance with the License.
    006     * You may obtain a copy of the License at
    007     *
    008     * http://www.apache.org/licenses/LICENSE-2.0
    009     *
    010     * Unless required by applicable law or agreed to in writing, software
    011     * distributed under the License is distributed on an "AS IS" BASIS,
    012     * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
    013     * See the License for the specific language governing permissions and
    014     * limitations under the License.
    015     */
    016
    017    package com.google.common.collect;
    018
    019    import com.google.common.annotations.Beta;
    020    import com.google.common.annotations.GwtCompatible;
    021
    022    import java.io.Serializable;
    023    import java.math.BigInteger;
    024
    025    /**
    026     * Factories for common {@link DiscreteDomain} instances.
    027     *
    028     * @author Gregory Kick
    029     * @since 10.0
    030     */
    031    @GwtCompatible
    032    @Beta
    033    public final class DiscreteDomains {
    034      private DiscreteDomains() {}
    035
    036      /**
    037       * Returns the discrete domain for values of type {@code Integer}.
    038       */
    039      public static DiscreteDomain<Integer> integers() {
    040        return IntegerDomain.INSTANCE;
    041      }
    042
    043      private static final class IntegerDomain extends DiscreteDomain<Integer>
    044          implements Serializable {
    045        private static final IntegerDomain INSTANCE = new IntegerDomain();
    046
    047        @Override public Integer next(Integer value) {
    048          int i = value;
    049          return (i == Integer.MAX_VALUE) ? null : i + 1;
    050        }
    051
    052        @Override public Integer previous(Integer value) {
    053          int i = value;
    054          return (i == Integer.MIN_VALUE) ? null : i - 1;
    055        }
    056
    057        @Override public long distance(Integer start, Integer end) {
    058          return (long) end - start;
    059        }
    060
    061        @Override public Integer minValue() {
    062          return Integer.MIN_VALUE;
    063        }
    064
    065        @Override public Integer maxValue() {
    066          return Integer.MAX_VALUE;
    067        }
    068
    069        private Object readResolve() {
    070          return INSTANCE;
    071        }
    072
    073        private static final long serialVersionUID = 0;
    074      }
    075
    076      /**
    077       * Returns the discrete domain for values of type {@code Long}.
    078       */
    079      public static DiscreteDomain<Long> longs() {
    080        return LongDomain.INSTANCE;
    081      }
    082
    083      private static final class LongDomain extends DiscreteDomain<Long>
    084          implements Serializable {
    085        private static final LongDomain INSTANCE = new LongDomain();
    086
    087        @Override public Long next(Long value) {
    088          long l = value;
    089          return (l == Long.MAX_VALUE) ? null : l + 1;
    090        }
    091
    092        @Override public Long previous(Long value) {
    093          long l = value;
    094          return (l == Long.MIN_VALUE) ? null : l - 1;
    095        }
    096
    097        @Override public long distance(Long start, Long end) {
    098          long result = end - start;
    099          if (end > start && result < 0) { // overflow
    100            return Long.MAX_VALUE;
    101          }
    102          if (end < start && result > 0) { // underflow
    103            return Long.MIN_VALUE;
    104          }
    105          return result;
    106        }
    107
    108        @Override public Long minValue() {
    109          return Long.MIN_VALUE;
    110        }
    111
    112        @Override public Long maxValue() {
    113          return Long.MAX_VALUE;
    114        }
    115
    116        private Object readResolve() {
    117          return INSTANCE;
    118        }
    119
    120        private static final long serialVersionUID = 0;
    121      }
    122
    123      /**
    124       * Returns the discrete domain for values of type {@code BigInteger}.
    125       */
    126      // TODO(kevinb): make sure it's tested, and make it public
    127      static DiscreteDomain<BigInteger> bigIntegers() {
    128        return BigIntegerDomain.INSTANCE;
    129      }
    130
    131      private static final class BigIntegerDomain extends DiscreteDomain<BigInteger>
    132          implements Serializable {
    133        private static final BigIntegerDomain INSTANCE = new BigIntegerDomain();
    134
    135        private static final BigInteger MIN_LONG =
    136            BigInteger.valueOf(Long.MIN_VALUE);
    137        private static final BigInteger MAX_LONG =
    138            BigInteger.valueOf(Long.MAX_VALUE);
    139
    140        @Override public BigInteger next(BigInteger value) {
    141          return value.add(BigInteger.ONE);
    142        }
    143
    144        @Override public BigInteger previous(BigInteger value) {
    145          return value.subtract(BigInteger.ONE);
    146        }
    147
    148        @Override public long distance(BigInteger start, BigInteger end) {
    149          return start.subtract(end).max(MIN_LONG).min(MAX_LONG).longValue();
    150        }
    151
    152        private Object readResolve() {
    153          return INSTANCE;
    154        }
    155
    156        private static final long serialVersionUID = 0;
    157      }
    158    }