001    /*
002     * Copyright (C) 2009 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.util.NoSuchElementException;
023    
024    /**
025     * A descriptor for a <i>discrete</i> {@code Comparable} domain such as all
026     * {@link Integer}s. A discrete domain is one that supports the three basic
027     * operations: {@link #next}, {@link #previous} and {@link #distance}, according
028     * to their specifications. The methods {@link #minValue} and {@link #maxValue}
029     * should also be overridden for bounded types.
030     *
031     * <p>A discrete domain always represents the <i>entire</i> set of values of its
032     * type; it cannot represent partial domains such as "prime integers" or
033     * "strings of length 5."
034     *
035     * <p>See the Guava User Guide section on <a href=
036     * "http://code.google.com/p/guava-libraries/wiki/RangesExplained#Discrete_Domains">
037     * {@code DiscreteDomain}</a>.
038     *
039     * @author Kevin Bourrillion
040     * @since 10.0
041     * @see DiscreteDomains
042     */
043    @GwtCompatible
044    @Beta
045    public abstract class DiscreteDomain<C extends Comparable> {
046      /** Constructor for use by subclasses. */
047      protected DiscreteDomain() {}
048    
049      /**
050       * Returns the unique least value of type {@code C} that is greater than
051       * {@code value}, or {@code null} if none exists. Inverse operation to {@link
052       * #previous}.
053       *
054       * @param value any value of type {@code C}
055       * @return the least value greater than {@code value}, or {@code null} if
056       *     {@code value} is {@code maxValue()}
057       */
058      public abstract C next(C value);
059    
060      /**
061       * Returns the unique greatest value of type {@code C} that is less than
062       * {@code value}, or {@code null} if none exists. Inverse operation to {@link
063       * #next}.
064       *
065       * @param value any value of type {@code C}
066       * @return the greatest value less than {@code value}, or {@code null} if
067       *     {@code value} is {@code minValue()}
068       */
069      public abstract C previous(C value);
070    
071      /**
072       * Returns a signed value indicating how many nested invocations of {@link
073       * #next} (if positive) or {@link #previous} (if negative) are needed to reach
074       * {@code end} starting from {@code start}. For example, if {@code end =
075       * next(next(next(start)))}, then {@code distance(start, end) == 3} and {@code
076       * distance(end, start) == -3}. As well, {@code distance(a, a)} is always
077       * zero.
078       *
079       * <p>Note that this function is necessarily well-defined for any discrete
080       * type.
081       *
082       * @return the distance as described above, or {@link Long#MIN_VALUE} or
083       *     {@link Long#MAX_VALUE} if the distance is too small or too large,
084       *     respectively.
085       */
086      public abstract long distance(C start, C end);
087    
088      /**
089       * Returns the minimum value of type {@code C}, if it has one. The minimum
090       * value is the unique value for which {@link Comparable#compareTo(Object)}
091       * never returns a positive value for any input of type {@code C}.
092       *
093       * <p>The default implementation throws {@code NoSuchElementException}.
094       *
095       * @return the minimum value of type {@code C}; never null
096       * @throws NoSuchElementException if the type has no (practical) minimum
097       *     value; for example, {@link java.math.BigInteger}
098       */
099      public C minValue() {
100        throw new NoSuchElementException();
101      }
102    
103      /**
104       * Returns the maximum value of type {@code C}, if it has one. The maximum
105       * value is the unique value for which {@link Comparable#compareTo(Object)}
106       * never returns a negative value for any input of type {@code C}.
107       *
108       * <p>The default implementation throws {@code NoSuchElementException}.
109       *
110       * @return the maximum value of type {@code C}; never null
111       * @throws NoSuchElementException if the type has no (practical) maximum
112       *     value; for example, {@link java.math.BigInteger}
113       */
114      public C maxValue() {
115        throw new NoSuchElementException();
116      }
117    }