Java tutorial
/* * Copyright (C) 2009 The Guava Authors * * Licensed 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 com.google.common.collect; import com.google.common.annotations.Beta; import com.google.common.annotations.GwtCompatible; import java.io.Serializable; import java.math.BigInteger; import java.util.NoSuchElementException; /** * A descriptor for a <i>discrete</i> {@code Comparable} domain such as all * {@link Integer} instances. A discrete domain is one that supports the three basic * operations: {@link #next}, {@link #previous} and {@link #distance}, according * to their specifications. The methods {@link #minValue} and {@link #maxValue} * should also be overridden for bounded types. * * <p>A discrete domain always represents the <i>entire</i> set of values of its * type; it cannot represent partial domains such as "prime integers" or * "strings of length 5." * * <p>See the Guava User Guide section on <a href= * "https://github.com/google/guava/wiki/RangesExplained#discrete-domains"> * {@code DiscreteDomain}</a>. * * @author Kevin Bourrillion * @since 10.0 */ @GwtCompatible @Beta public abstract class DiscreteDomain<C extends Comparable> { /** * Returns the discrete domain for values of type {@code Integer}. * * @since 14.0 (since 10.0 as {@code DiscreteDomains.integers()}) */ public static DiscreteDomain<Integer> integers() { return IntegerDomain.INSTANCE; } private static final class IntegerDomain extends DiscreteDomain<Integer> implements Serializable { private static final IntegerDomain INSTANCE = new IntegerDomain(); @Override public Integer next(Integer value) { int i = value; return (i == Integer.MAX_VALUE) ? null : i + 1; } @Override public Integer previous(Integer value) { int i = value; return (i == Integer.MIN_VALUE) ? null : i - 1; } @Override public long distance(Integer start, Integer end) { return (long) end - start; } @Override public Integer minValue() { return Integer.MIN_VALUE; } @Override public Integer maxValue() { return Integer.MAX_VALUE; } private Object readResolve() { return INSTANCE; } @Override public String toString() { return "DiscreteDomain.integers()"; } private static final long serialVersionUID = 0; } /** * Returns the discrete domain for values of type {@code Long}. * * @since 14.0 (since 10.0 as {@code DiscreteDomains.longs()}) */ public static DiscreteDomain<Long> longs() { return LongDomain.INSTANCE; } private static final class LongDomain extends DiscreteDomain<Long> implements Serializable { private static final LongDomain INSTANCE = new LongDomain(); @Override public Long next(Long value) { long l = value; return (l == Long.MAX_VALUE) ? null : l + 1; } @Override public Long previous(Long value) { long l = value; return (l == Long.MIN_VALUE) ? null : l - 1; } @Override public long distance(Long start, Long end) { long result = end - start; if (end > start && result < 0) { // overflow return Long.MAX_VALUE; } if (end < start && result > 0) { // underflow return Long.MIN_VALUE; } return result; } @Override public Long minValue() { return Long.MIN_VALUE; } @Override public Long maxValue() { return Long.MAX_VALUE; } private Object readResolve() { return INSTANCE; } @Override public String toString() { return "DiscreteDomain.longs()"; } private static final long serialVersionUID = 0; } /** * Returns the discrete domain for values of type {@code BigInteger}. * * @since 15.0 */ public static DiscreteDomain<BigInteger> bigIntegers() { return BigIntegerDomain.INSTANCE; } private static final class BigIntegerDomain extends DiscreteDomain<BigInteger> implements Serializable { private static final BigIntegerDomain INSTANCE = new BigIntegerDomain(); private static final BigInteger MIN_LONG = BigInteger.valueOf(Long.MIN_VALUE); private static final BigInteger MAX_LONG = BigInteger.valueOf(Long.MAX_VALUE); @Override public BigInteger next(BigInteger value) { return value.add(BigInteger.ONE); } @Override public BigInteger previous(BigInteger value) { return value.subtract(BigInteger.ONE); } @Override public long distance(BigInteger start, BigInteger end) { return end.subtract(start).max(MIN_LONG).min(MAX_LONG).longValue(); } private Object readResolve() { return INSTANCE; } @Override public String toString() { return "DiscreteDomain.bigIntegers()"; } private static final long serialVersionUID = 0; } /** Constructor for use by subclasses. */ protected DiscreteDomain() { } /** * Returns the unique least value of type {@code C} that is greater than * {@code value}, or {@code null} if none exists. Inverse operation to {@link * #previous}. * * @param value any value of type {@code C} * @return the least value greater than {@code value}, or {@code null} if * {@code value} is {@code maxValue()} */ public abstract C next(C value); /** * Returns the unique greatest value of type {@code C} that is less than * {@code value}, or {@code null} if none exists. Inverse operation to {@link * #next}. * * @param value any value of type {@code C} * @return the greatest value less than {@code value}, or {@code null} if * {@code value} is {@code minValue()} */ public abstract C previous(C value); /** * Returns a signed value indicating how many nested invocations of {@link * #next} (if positive) or {@link #previous} (if negative) are needed to reach * {@code end} starting from {@code start}. For example, if {@code end = * next(next(next(start)))}, then {@code distance(start, end) == 3} and {@code * distance(end, start) == -3}. As well, {@code distance(a, a)} is always * zero. * * <p>Note that this function is necessarily well-defined for any discrete * type. * * @return the distance as described above, or {@link Long#MIN_VALUE} or * {@link Long#MAX_VALUE} if the distance is too small or too large, * respectively. */ public abstract long distance(C start, C end); /** * Returns the minimum value of type {@code C}, if it has one. The minimum * value is the unique value for which {@link Comparable#compareTo(Object)} * never returns a positive value for any input of type {@code C}. * * <p>The default implementation throws {@code NoSuchElementException}. * * @return the minimum value of type {@code C}; never null * @throws NoSuchElementException if the type has no (practical) minimum * value; for example, {@link java.math.BigInteger} */ public C minValue() { throw new NoSuchElementException(); } /** * Returns the maximum value of type {@code C}, if it has one. The maximum * value is the unique value for which {@link Comparable#compareTo(Object)} * never returns a negative value for any input of type {@code C}. * * <p>The default implementation throws {@code NoSuchElementException}. * * @return the maximum value of type {@code C}; never null * @throws NoSuchElementException if the type has no (practical) maximum * value; for example, {@link java.math.BigInteger} */ public C maxValue() { throw new NoSuchElementException(); } }