DiscreteDomain.java
/*
* 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 static com.google.common.base.Preconditions.checkArgument;
import static com.google.common.collect.CollectPreconditions.checkNonnegative;
import com.google.common.annotations.GwtCompatible;
import com.google.common.primitives.Ints;
import com.google.errorprone.annotations.CanIgnoreReturnValue;
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
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();
IntegerDomain() {
super(true);
}
@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
Integer offset(Integer origin, long distance) {
checkNonnegative(distance, "distance");
return Ints.checkedCast(origin.longValue() + distance);
}
@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();
LongDomain() {
super(true);
}
@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
Long offset(Long origin, long distance) {
checkNonnegative(distance, "distance");
long result = origin + distance;
if (result < 0) {
checkArgument(origin < 0, "overflow");
}
return result;
}
@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();
BigIntegerDomain() {
super(true);
}
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
BigInteger offset(BigInteger origin, long distance) {
checkNonnegative(distance, "distance");
return origin.add(BigInteger.valueOf(distance));
}
@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;
}
final boolean supportsFastOffset;
/** Constructor for use by subclasses. */
protected DiscreteDomain() {
this(false);
}
/** Private constructor for built-in DiscreteDomains supporting fast offset. */
private DiscreteDomain(boolean supportsFastOffset) {
this.supportsFastOffset = supportsFastOffset;
}
/**
* Returns, conceptually, "origin + distance", or equivalently, the result of calling {@link
* #next} on {@code origin} {@code distance} times.
*/
C offset(C origin, long distance) {
checkNonnegative(distance, "distance");
for (long i = 0; i < distance; i++) {
origin = next(origin);
}
return origin;
}
/**
* 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}
*/
@CanIgnoreReturnValue
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}
*/
@CanIgnoreReturnValue
public C maxValue() {
throw new NoSuchElementException();
}
}