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The Range.java Java example source code
/*
* Copyright (C) 2008 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.checkNotNull;
import com.google.common.annotations.GwtCompatible;
import com.google.common.base.Equivalence;
import com.google.common.base.Function;
import com.google.common.base.Predicate;
import java.io.Serializable;
import java.util.Comparator;
import java.util.Iterator;
import java.util.NoSuchElementException;
import java.util.SortedSet;
import javax.annotation.Nullable;
/**
* A range (or "interval") defines the <i>boundaries around a contiguous span of values of some
* {@code Comparable} type; for example, "integers from 1 to 100 inclusive." Note that it is not
* possible to <i>iterate over these contained values. To do so, pass this range instance and
* an appropriate {@link DiscreteDomain} to {@link ContiguousSet#create}.
*
* <h3>Types of ranges
*
* <p>Each end of the range may be bounded or unbounded. If bounded, there is an associated
* <i>endpoint value, and the range is considered to be either open (does not include the
* endpoint) or <i>closed (includes the endpoint) on that side. With three possibilities on each
* side, this yields nine basic types of ranges, enumerated below. (Notation: a square bracket
* ({@code [ ]}) indicates that the range is closed on that side; a parenthesis ({@code ( )}) means
* it is either open or unbounded. The construct {@code {x | statement}} is read "the set of all
* <i>x such that statement.")
*
* <blockquote>
* <table>
* <tr> | Notation | Definition | Factory method
* <tr> | {@code (a..b)} | {@code {x | a < x < b}} | {@link Range#open open}
* <tr> | {@code [a..b]} | {@code {x | a <= x <= b}} | {@link Range#closed closed}
* <tr> | {@code (a..b]} | {@code {x | a < x <= b}} | {@link Range#openClosed openClosed}
* <tr> | {@code [a..b)} | {@code {x | a <= x < b}} | {@link Range#closedOpen closedOpen}
* <tr> | {@code (a..+∞)} | {@code {x | x > a}} | {@link Range#greaterThan greaterThan}
* <tr> | {@code [a..+∞)} | {@code {x | x >= a}} | {@link Range#atLeast atLeast}
* <tr> | {@code (-∞..b)} | {@code {x | x < b}} | {@link Range#lessThan lessThan}
* <tr> | {@code (-∞..b]} | {@code {x | x <= b}} | {@link Range#atMost atMost}
* <tr> | {@code (-∞..+∞)} | {@code {x}} | {@link Range#all all}
* </table>
* </blockquote>
*
* <p>When both endpoints exist, the upper endpoint may not be less than the lower. The endpoints
* may be equal only if at least one of the bounds is closed:
*
* <ul>
* <li>{@code [a..a]} : a singleton range
* <li>{@code [a..a); (a..a]} : {@linkplain #isEmpty empty} ranges; also valid
* <li>{@code (a..a)} : invalid; an exception will be thrown
* </ul>
*
* <h3>Warnings
*
* <ul>
* <li>Use immutable value types only, if at all possible. If you must use a mutable type, do
* not</b> allow the endpoint instances to mutate after the range is created!
* <li>Your value type's comparison method should be {@linkplain Comparable consistent with equals}
* if at all possible. Otherwise, be aware that concepts used throughout this documentation such
* as "equal", "same", "unique" and so on actually refer to whether {@link Comparable#compareTo
* compareTo} returns zero, not whether {@link Object#equals equals} returns {@code true}.
* <li>A class which implements {@code Comparable} is very broken, and will cause
* undefined horrible things to happen in {@code Range}. For now, the Range API does not prevent
* its use, because this would also rule out all ungenerified (pre-JDK1.5) data types. <b>This
* may change in the future.</b>
* </ul>
*
* <h3>Other notes
*
* <ul>
* <li>Instances of this type are obtained using the static factory methods in this class.
* <li>Ranges are convex: whenever two values are contained, all values in between them must
* also be contained. More formally, for any {@code c1 <= c2 <= c3} of type {@code C}, {@code
* r.contains(c1) && r.contains(c3)} implies {@code r.contains(c2)}). This means that a {@code
* Range<Integer>} can never be used to represent, say, "all prime numbers from 1 to
* 100."
* <li>When evaluated as a {@link Predicate}, a range yields the same result as invoking {@link
* #contains}.
* <li>Terminology note: a range {@code a} is said to be the maximal range having property
* <i>P if, for all ranges {@code b} also having property P, {@code a.encloses(b)}.
* Likewise, {@code a} is <i>minimal when {@code b.encloses(a)} for all {@code b} having
* property <i>P. See, for example, the definition of {@link #intersection intersection}.
* </ul>
*
* <h3>Further reading
*
* <p>See the Guava User Guide article on
* <a href="https://github.com/google/guava/wiki/RangesExplained">{@code Range}.
*
* @author Kevin Bourrillion
* @author Gregory Kick
* @since 10.0
*/
@GwtCompatible
@SuppressWarnings("rawtypes")
public final class Range<C extends Comparable> implements Predicate, Serializable {
private static final Function<Range, Cut> LOWER_BOUND_FN =
new Function<Range, Cut>() {
@Override
public Cut apply(Range range) {
return range.lowerBound;
}
};
@SuppressWarnings("unchecked")
static <C extends Comparable Function, Cut> lowerBoundFn() {
return (Function) LOWER_BOUND_FN;
}
private static final Function<Range, Cut> UPPER_BOUND_FN =
new Function<Range, Cut>() {
@Override
public Cut apply(Range range) {
return range.upperBound;
}
};
@SuppressWarnings("unchecked")
static <C extends Comparable Function, Cut> upperBoundFn() {
return (Function) UPPER_BOUND_FN;
}
static final Ordering<Range RANGE_LEX_ORDERING = new RangeLexOrdering();
static <C extends Comparable Range create(Cut lowerBound, Cut upperBound) {
return new Range<C>(lowerBound, upperBound);
}
/**
* Returns a range that contains all values strictly greater than {@code
* lower} and strictly less than {@code upper}.
*
* @throws IllegalArgumentException if {@code lower} is greater than <i>or
* equal to</i> {@code upper}
* @since 14.0
*/
public static <C extends Comparable Range open(C lower, C upper) {
return create(Cut.aboveValue(lower), Cut.belowValue(upper));
}
/**
* Returns a range that contains all values greater than or equal to
* {@code lower} and less than or equal to {@code upper}.
*
* @throws IllegalArgumentException if {@code lower} is greater than {@code
* upper}
* @since 14.0
*/
public static <C extends Comparable Range closed(C lower, C upper) {
return create(Cut.belowValue(lower), Cut.aboveValue(upper));
}
/**
* Returns a range that contains all values greater than or equal to
* {@code lower} and strictly less than {@code upper}.
*
* @throws IllegalArgumentException if {@code lower} is greater than {@code
* upper}
* @since 14.0
*/
public static <C extends Comparable Range closedOpen(C lower, C upper) {
return create(Cut.belowValue(lower), Cut.belowValue(upper));
}
/**
* Returns a range that contains all values strictly greater than {@code
* lower} and less than or equal to {@code upper}.
*
* @throws IllegalArgumentException if {@code lower} is greater than {@code
* upper}
* @since 14.0
*/
public static <C extends Comparable Range openClosed(C lower, C upper) {
return create(Cut.aboveValue(lower), Cut.aboveValue(upper));
}
/**
* Returns a range that contains any value from {@code lower} to {@code
* upper}, where each endpoint may be either inclusive (closed) or exclusive
* (open).
*
* @throws IllegalArgumentException if {@code lower} is greater than {@code
* upper}
* @since 14.0
*/
public static <C extends Comparable Range range(
C lower, BoundType lowerType, C upper, BoundType upperType) {
checkNotNull(lowerType);
checkNotNull(upperType);
Cut<C> lowerBound =
(lowerType == BoundType.OPEN) ? Cut.aboveValue(lower) : Cut.belowValue(lower);
Cut<C> upperBound =
(upperType == BoundType.OPEN) ? Cut.belowValue(upper) : Cut.aboveValue(upper);
return create(lowerBound, upperBound);
}
/**
* Returns a range that contains all values strictly less than {@code
* endpoint}.
*
* @since 14.0
*/
public static <C extends Comparable Range lessThan(C endpoint) {
return create(Cut.<C>belowAll(), Cut.belowValue(endpoint));
}
/**
* Returns a range that contains all values less than or equal to
* {@code endpoint}.
*
* @since 14.0
*/
public static <C extends Comparable Range atMost(C endpoint) {
return create(Cut.<C>belowAll(), Cut.aboveValue(endpoint));
}
/**
* Returns a range with no lower bound up to the given endpoint, which may be
* either inclusive (closed) or exclusive (open).
*
* @since 14.0
*/
public static <C extends Comparable Range upTo(C endpoint, BoundType boundType) {
switch (boundType) {
case OPEN:
return lessThan(endpoint);
case CLOSED:
return atMost(endpoint);
default:
throw new AssertionError();
}
}
/**
* Returns a range that contains all values strictly greater than {@code
* endpoint}.
*
* @since 14.0
*/
public static <C extends Comparable Range greaterThan(C endpoint) {
return create(Cut.aboveValue(endpoint), Cut.<C>aboveAll());
}
/**
* Returns a range that contains all values greater than or equal to
* {@code endpoint}.
*
* @since 14.0
*/
public static <C extends Comparable Range atLeast(C endpoint) {
return create(Cut.belowValue(endpoint), Cut.<C>aboveAll());
}
/**
* Returns a range from the given endpoint, which may be either inclusive
* (closed) or exclusive (open), with no upper bound.
*
* @since 14.0
*/
public static <C extends Comparable Range downTo(C endpoint, BoundType boundType) {
switch (boundType) {
case OPEN:
return greaterThan(endpoint);
case CLOSED:
return atLeast(endpoint);
default:
throw new AssertionError();
}
}
private static final Range<Comparable> ALL =
new Range<Comparable>(Cut.belowAll(), Cut.aboveAll());
/**
* Returns a range that contains every value of type {@code C}.
*
* @since 14.0
*/
@SuppressWarnings("unchecked")
public static <C extends Comparable Range all() {
return (Range) ALL;
}
/**
* Returns a range that {@linkplain Range#contains(Comparable) contains} only
* the given value. The returned range is {@linkplain BoundType#CLOSED closed}
* on both ends.
*
* @since 14.0
*/
public static <C extends Comparable Range singleton(C value) {
return closed(value, value);
}
/**
* Returns the minimal range that
* {@linkplain Range#contains(Comparable) contains} all of the given values.
* The returned range is {@linkplain BoundType#CLOSED closed} on both ends.
*
* @throws ClassCastException if the parameters are not <i>mutually
* comparable</i>
* @throws NoSuchElementException if {@code values} is empty
* @throws NullPointerException if any of {@code values} is null
* @since 14.0
*/
public static <C extends Comparable Range encloseAll(Iterable values) {
checkNotNull(values);
if (values instanceof ContiguousSet) {
return ((ContiguousSet<C>) values).range();
}
Iterator<C> valueIterator = values.iterator();
C min = checkNotNull(valueIterator.next());
C max = min;
while (valueIterator.hasNext()) {
C value = checkNotNull(valueIterator.next());
min = Ordering.natural().min(min, value);
max = Ordering.natural().max(max, value);
}
return closed(min, max);
}
final Cut<C> lowerBound;
final Cut<C> upperBound;
private Range(Cut<C> lowerBound, Cut upperBound) {
this.lowerBound = checkNotNull(lowerBound);
this.upperBound = checkNotNull(upperBound);
if (lowerBound.compareTo(upperBound) > 0
|| lowerBound == Cut.<C>aboveAll()
|| upperBound == Cut.<C>belowAll()) {
throw new IllegalArgumentException("Invalid range: " + toString(lowerBound, upperBound));
}
}
/**
* Returns {@code true} if this range has a lower endpoint.
*/
public boolean hasLowerBound() {
return lowerBound != Cut.belowAll();
}
/**
* Returns the lower endpoint of this range.
*
* @throws IllegalStateException if this range is unbounded below (that is, {@link
* #hasLowerBound()} returns {@code false})
*/
public C lowerEndpoint() {
return lowerBound.endpoint();
}
/**
* Returns the type of this range's lower bound: {@link BoundType#CLOSED} if the range includes
* its lower endpoint, {@link BoundType#OPEN} if it does not.
*
* @throws IllegalStateException if this range is unbounded below (that is, {@link
* #hasLowerBound()} returns {@code false})
*/
public BoundType lowerBoundType() {
return lowerBound.typeAsLowerBound();
}
/**
* Returns {@code true} if this range has an upper endpoint.
*/
public boolean hasUpperBound() {
return upperBound != Cut.aboveAll();
}
/**
* Returns the upper endpoint of this range.
*
* @throws IllegalStateException if this range is unbounded above (that is, {@link
* #hasUpperBound()} returns {@code false})
*/
public C upperEndpoint() {
return upperBound.endpoint();
}
/**
* Returns the type of this range's upper bound: {@link BoundType#CLOSED} if the range includes
* its upper endpoint, {@link BoundType#OPEN} if it does not.
*
* @throws IllegalStateException if this range is unbounded above (that is, {@link
* #hasUpperBound()} returns {@code false})
*/
public BoundType upperBoundType() {
return upperBound.typeAsUpperBound();
}
/**
* Returns {@code true} if this range is of the form {@code [v..v)} or {@code (v..v]}. (This does
* not encompass ranges of the form {@code (v..v)}, because such ranges are <i>invalid and
* can't be constructed at all.)
*
* <p>Note that certain discrete ranges such as the integer range {@code (3..4)} are not
* considered empty, even though they contain no actual values. In these cases, it may be
* helpful to preprocess ranges with {@link #canonical(DiscreteDomain)}.
*/
public boolean isEmpty() {
return lowerBound.equals(upperBound);
}
/**
* Returns {@code true} if {@code value} is within the bounds of this range. For example, on the
* range {@code [0..2)}, {@code contains(1)} returns {@code true}, while {@code contains(2)}
* returns {@code false}.
*/
public boolean contains(C value) {
checkNotNull(value);
// let this throw CCE if there is some trickery going on
return lowerBound.isLessThan(value) && !upperBound.isLessThan(value);
}
/**
* @deprecated Provided only to satisfy the {@link Predicate} interface; use {@link #contains}
* instead.
*/
@Deprecated
@Override
public boolean apply(C input) {
return contains(input);
}
/**
* Returns {@code true} if every element in {@code values} is {@linkplain #contains contained} in
* this range.
*/
public boolean containsAll(Iterable<? extends C> values) {
if (Iterables.isEmpty(values)) {
return true;
}
// this optimizes testing equality of two range-backed sets
if (values instanceof SortedSet) {
SortedSet<? extends C> set = cast(values);
Comparator<?> comparator = set.comparator();
if (Ordering.natural().equals(comparator) || comparator == null) {
return contains(set.first()) && contains(set.last());
}
}
for (C value : values) {
if (!contains(value)) {
return false;
}
}
return true;
}
/**
* Returns {@code true} if the bounds of {@code other} do not extend outside the bounds of this
* range. Examples:
*
* <ul>
* <li>{@code [3..6]} encloses {@code [4..5]}
* <li>{@code (3..6)} encloses {@code (3..6)}
* <li>{@code [3..6]} encloses {@code [4..4)} (even though the latter is empty)
* <li>{@code (3..6]} does not enclose {@code [3..6]}
* <li>{@code [4..5]} does not enclose {@code (3..6)} (even though it contains every value
* contained by the latter range)
* <li>{@code [3..6]} does not enclose {@code (1..1]} (even though it contains every value
* contained by the latter range)
* </ul>
*
* <p>Note that if {@code a.encloses(b)}, then {@code b.contains(v)} implies
* {@code a.contains(v)}, but as the last two examples illustrate, the converse is not always
* true.
*
* <p>Being reflexive, antisymmetric and transitive, the {@code encloses} relation defines a
* <i>partial order over ranges. There exists a unique {@linkplain Range#all maximal} range
* according to this relation, and also numerous {@linkplain #isEmpty minimal} ranges. Enclosure
* also implies {@linkplain #isConnected connectedness}.
*/
public boolean encloses(Range<C> other) {
return lowerBound.compareTo(other.lowerBound) <= 0
&& upperBound.compareTo(other.upperBound) >= 0;
}
/**
* Returns {@code true} if there exists a (possibly empty) range which is {@linkplain #encloses
* enclosed} by both this range and {@code other}.
*
* <p>For example,
* <ul>
* <li>{@code [2, 4)} and {@code [5, 7)} are not connected
* <li>{@code [2, 4)} and {@code [3, 5)} are connected, because both enclose {@code [3, 4)}
* <li>{@code [2, 4)} and {@code [4, 6)} are connected, because both enclose the empty range
* {@code [4, 4)}
* </ul>
*
* <p>Note that this range and {@code other} have a well-defined {@linkplain #span union} and
* {@linkplain #intersection intersection} (as a single, possibly-empty range) if and only if this
* method returns {@code true}.
*
* <p>The connectedness relation is both reflexive and symmetric, but does not form an {@linkplain
* Equivalence equivalence relation} as it is not transitive.
*
* <p>Note that certain discrete ranges are not considered connected, even though there are no
* elements "between them." For example, {@code [3, 5]} is not considered connected to {@code
* [6, 10]}. In these cases, it may be desirable for both input ranges to be preprocessed with
* {@link #canonical(DiscreteDomain)} before testing for connectedness.
*/
public boolean isConnected(Range<C> other) {
return lowerBound.compareTo(other.upperBound) <= 0
&& other.lowerBound.compareTo(upperBound) <= 0;
}
/**
* Returns the maximal range {@linkplain #encloses enclosed} by both this range and {@code
* connectedRange}, if such a range exists.
*
* <p>For example, the intersection of {@code [1..5]} and {@code (3..7)} is {@code (3..5]}. The
* resulting range may be empty; for example, {@code [1..5)} intersected with {@code [5..7)}
* yields the empty range {@code [5..5)}.
*
* <p>The intersection exists if and only if the two ranges are {@linkplain #isConnected
* connected}.
*
* <p>The intersection operation is commutative, associative and idempotent, and its identity
* element is {@link Range#all}).
*
* @throws IllegalArgumentException if {@code isConnected(connectedRange)} is {@code false}
*/
public Range<C> intersection(Range connectedRange) {
int lowerCmp = lowerBound.compareTo(connectedRange.lowerBound);
int upperCmp = upperBound.compareTo(connectedRange.upperBound);
if (lowerCmp >= 0 && upperCmp <= 0) {
return this;
} else if (lowerCmp <= 0 && upperCmp >= 0) {
return connectedRange;
} else {
Cut<C> newLower = (lowerCmp >= 0) ? lowerBound : connectedRange.lowerBound;
Cut<C> newUpper = (upperCmp <= 0) ? upperBound : connectedRange.upperBound;
return create(newLower, newUpper);
}
}
/**
* Returns the minimal range that {@linkplain #encloses encloses} both this range and {@code
* other}. For example, the span of {@code [1..3]} and {@code (5..7)} is {@code [1..7)}.
*
* <p>If the input ranges are {@linkplain #isConnected connected}, the returned range can
* also be called their <i>union. If they are not, note that the span might contain values
* that are not contained in either input range.
*
* <p>Like {@link #intersection(Range) intersection}, this operation is commutative, associative
* and idempotent. Unlike it, it is always well-defined for any two input ranges.
*/
public Range<C> span(Range other) {
int lowerCmp = lowerBound.compareTo(other.lowerBound);
int upperCmp = upperBound.compareTo(other.upperBound);
if (lowerCmp <= 0 && upperCmp >= 0) {
return this;
} else if (lowerCmp >= 0 && upperCmp <= 0) {
return other;
} else {
Cut<C> newLower = (lowerCmp <= 0) ? lowerBound : other.lowerBound;
Cut<C> newUpper = (upperCmp >= 0) ? upperBound : other.upperBound;
return create(newLower, newUpper);
}
}
/**
* Returns the canonical form of this range in the given domain. The canonical form has the
* following properties:
*
* <ul>
* <li>equivalence: {@code a.canonical().contains(v) == a.contains(v)} for all {@code v} (in other
* words, {@code ContiguousSet.create(a.canonical(domain), domain).equals(
* ContiguousSet.create(a, domain))}
* <li>uniqueness: unless {@code a.isEmpty()},
* {@code ContiguousSet.create(a, domain).equals(ContiguousSet.create(b, domain))} implies
* {@code a.canonical(domain).equals(b.canonical(domain))}
* <li>idempotence: {@code a.canonical(domain).canonical(domain).equals(a.canonical(domain))}
* </ul>
*
* <p>Furthermore, this method guarantees that the range returned will be one of the following
* canonical forms:
*
* <ul>
* <li>[start..end)
* <li>[start..+∞)
* <li>(-∞..end) (only if type {@code C} is unbounded below)
* <li>(-∞..+∞) (only if type {@code C} is unbounded below)
* </ul>
*/
public Range<C> canonical(DiscreteDomain domain) {
checkNotNull(domain);
Cut<C> lower = lowerBound.canonical(domain);
Cut<C> upper = upperBound.canonical(domain);
return (lower == lowerBound && upper == upperBound) ? this : create(lower, upper);
}
/**
* Returns {@code true} if {@code object} is a range having the same endpoints and bound types as
* this range. Note that discrete ranges such as {@code (1..4)} and {@code [2..3]} are <b>not
* equal to one another, despite the fact that they each contain precisely the same set of values.
* Similarly, empty ranges are not equal unless they have exactly the same representation, so
* {@code [3..3)}, {@code (3..3]}, {@code (4..4]} are all unequal.
*/
@Override
public boolean equals(@Nullable Object object) {
if (object instanceof Range) {
Range<?> other = (Range) object;
return lowerBound.equals(other.lowerBound) && upperBound.equals(other.upperBound);
}
return false;
}
/** Returns a hash code for this range. */
@Override
public int hashCode() {
return lowerBound.hashCode() * 31 + upperBound.hashCode();
}
/**
* Returns a string representation of this range, such as {@code "[3..5)"} (other examples are
* listed in the class documentation).
*/
@Override
public String toString() {
return toString(lowerBound, upperBound);
}
private static String toString(Cut<?> lowerBound, Cut upperBound) {
StringBuilder sb = new StringBuilder(16);
lowerBound.describeAsLowerBound(sb);
sb.append("..");
upperBound.describeAsUpperBound(sb);
return sb.toString();
}
/**
* Used to avoid http://bugs.sun.com/view_bug.do?bug_id=6558557
*/
private static <T> SortedSet cast(Iterable iterable) {
return (SortedSet<T>) iterable;
}
Object readResolve() {
if (this.equals(ALL)) {
return all();
} else {
return this;
}
}
@SuppressWarnings("unchecked") // this method may throw CCE
static int compareOrThrow(Comparable left, Comparable right) {
return left.compareTo(right);
}
/**
* Needed to serialize sorted collections of Ranges.
*/
private static class RangeLexOrdering extends Ordering<Range implements Serializable {
@Override
public int compare(Range<?> left, Range right) {
return ComparisonChain.start()
.compare(left.lowerBound, right.lowerBound)
.compare(left.upperBound, right.upperBound)
.result();
}
private static final long serialVersionUID = 0;
}
private static final long serialVersionUID = 0;
}
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