com.google.common.collect.Range Maven / Gradle / Ivy
/*
* 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 static com.google.common.collect.Ranges.create;
import com.google.common.annotations.Beta;
import com.google.common.annotations.GwtCompatible;
import com.google.common.base.Equivalence;
import com.google.common.base.Predicate;
import java.io.Serializable;
import java.util.Collections;
import java.util.Comparator;
import java.util.Set;
import java.util.SortedSet;
import javax.annotation.Nullable;
/**
* A range (or "interval") defines the 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 iterate over these contained values unless an appropriate {@link
* DiscreteDomain} can be provided to the {@link #asSet asSet} method.
*
* Types of ranges
*
* Each end of the range may be bounded or unbounded. If bounded, there is an associated
* endpoint value, and the range is considered to be either open (does not include the
* endpoint) or 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
* x such that statement.")
*
*
* Notation Definition Factory method
* {@code (a..b)} {@code {x | a < x < b}} {@link Ranges#open open}
* {@code [a..b]} {@code {x | a <= x <= b}} {@link Ranges#closed closed}
* {@code (a..b]} {@code {x | a < x <= b}} {@link Ranges#openClosed openClosed}
* {@code [a..b)} {@code {x | a <= x < b}} {@link Ranges#closedOpen closedOpen}
* {@code (a..+∞)} {@code {x | x > a}} {@link Ranges#greaterThan greaterThan}
* {@code [a..+∞)} {@code {x | x >= a}} {@link Ranges#atLeast atLeast}
* {@code (-∞..b)} {@code {x | x < b}} {@link Ranges#lessThan lessThan}
* {@code (-∞..b]} {@code {x | x <= b}} {@link Ranges#atMost atMost}
* {@code (-∞..+∞)} {@code {x}} {@link Ranges#all all}
*
*
* 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:
*
*
* - {@code [a..a]} : a singleton range
*
- {@code [a..a); (a..a]} : {@linkplain #isEmpty empty} ranges; also valid
*
- {@code (a..a)} : invalid; an exception will be thrown
*
*
* Warnings
*
*
* - Use immutable value types only, if at all possible. If you must use a mutable type, do
* not allow the endpoint instances to mutate after the range is created!
*
- 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}.
*
- 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. This
* may change in the future.
*
*
* Other notes
*
*
* - Instances of this type are obtained using the static factory methods in the {@link Ranges}
* class.
*
- 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
} can never be used to represent, say, "all prime numbers from 1 to
* 100."
* - When evaluated as a {@link Predicate}, a range yields the same result as invoking {@link
* #contains}.
*
- Terminology note: a range {@code a} is said to be the maximal range having property
* P if, for all ranges {@code b} also having property P, {@code a.encloses(b)}.
* Likewise, {@code a} is minimal when {@code b.encloses(a)} for all {@code b} having
* property P. See, for example, the definition of {@link #intersection intersection}.
*
*
* Further reading
*
* See the Guava User Guide article on
* {@code Range}.
*
* @author Kevin Bourrillion
* @author Gregory Kick
* @since 10.0
*/
@Beta
@GwtCompatible
@SuppressWarnings("rawtypes")
public final class Range implements Predicate, Serializable {
final Cut lowerBound;
final Cut upperBound;
Range(Cut lowerBound, Cut upperBound) {
if (lowerBound.compareTo(upperBound) > 0) {
throw new IllegalArgumentException("Invalid range: " + toString(lowerBound, upperBound));
}
this.lowerBound = lowerBound;
this.upperBound = 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 invalid and
* can't be constructed at all.)
*
* Note that certain discrete ranges such as the integer range {@code (3..4)} are not
* considered empty, even though they contain no actual values.
*/
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);
}
/**
* Equivalent to {@link #contains}; provided only to satisfy the {@link Predicate} interface. When
* using a reference of type {@code Range}, always invoke {@link #contains} directly instead.
*/
@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 values) {
if (Iterables.isEmpty(values)) {
return true;
}
// this optimizes testing equality of two range-backed sets
if (values instanceof SortedSet) {
SortedSet 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:
*
*
* - {@code [3..6]} encloses {@code [4..5]}
*
- {@code (3..6)} encloses {@code (3..6)}
*
- {@code [3..6]} encloses {@code [4..4)} (even though the latter is empty)
*
- {@code (3..6]} does not enclose {@code [3..6]}
*
- {@code [4..5]} does not enclose {@code (3..6)} (even though it contains every value
* contained by the latter range)
*
- {@code [3..6]} does not enclose {@code (1..1]} (even though it contains every value
* contained by the latter range)
*
*
* 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.
*
* Being reflexive, antisymmetric and transitive, the {@code encloses} relation defines a
* partial order over ranges. There exists a unique {@linkplain Ranges#all maximal} range
* according to this relation, and also numerous {@linkplain #isEmpty minimal} ranges. Enclosure
* also implies {@linkplain #isConnected connectedness}.
*/
public boolean encloses(Range 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}.
*
* For example,
*
* - {@code [2, 4)} and {@code [5, 7)} are not connected
*
- {@code [2, 4)} and {@code [3, 5)} are connected, because both enclose {@code [3, 4)}
*
- {@code [2, 4)} and {@code [4, 6)} are connected, because both enclose the empty range
* {@code [4, 4)}
*
*
* 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}.
*
*
The connectedness relation is both reflexive and symmetric, but does not form an {@linkplain
* Equivalence equivalence relation} as it is not transitive.
*/
public boolean isConnected(Range 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.
*
* 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)}.
*
*
The intersection exists if and only if the two ranges are {@linkplain #isConnected
* connected}.
*
*
The intersection operation is commutative, associative and idempotent, and its identity
* element is {@link Ranges#all}).
*
* @throws IllegalArgumentException if {@code isConnected(connectedRange)} is {@code false}
*/
public Range intersection(Range connectedRange) {
Cut newLower = Ordering.natural().max(lowerBound, connectedRange.lowerBound);
Cut newUpper = Ordering.natural().min(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)}.
*
* If the input ranges are {@linkplain #isConnected connected}, the returned range can
* also be called their union. If they are not, note that the span might contain values
* that are not contained in either input range.
*
*
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 span(Range other) {
Cut newLower = Ordering.natural().min(lowerBound, other.lowerBound);
Cut newUpper = Ordering.natural().max(upperBound, other.upperBound);
return create(newLower, newUpper);
}
/**
* Returns an {@link ContiguousSet} containing the same values in the given domain
* {@linkplain Range#contains contained} by this range.
*
* Note: {@code a.asSet(d).equals(b.asSet(d))} does not imply {@code a.equals(b)}! For
* example, {@code a} and {@code b} could be {@code [2..4]} and {@code (1..5)}, or the empty
* ranges {@code [3..3)} and {@code [4..4)}.
*
*
Warning: Be extremely careful what you do with the {@code asSet} view of a large
* range (such as {@code Ranges.greaterThan(0)}). Certain operations on such a set can be
* performed efficiently, but others (such as {@link Set#hashCode} or {@link
* Collections#frequency}) can cause major performance problems.
*
*
The returned set's {@link Object#toString} method returns a short-hand form of the set's
* contents, such as {@code "[1..100]}"}.
*
* @throws IllegalArgumentException if neither this range nor the domain has a lower bound, or if
* neither has an upper bound
*/
// TODO(kevinb): commit in spec to which methods are efficient?
@GwtCompatible(serializable = false)
public ContiguousSet asSet(DiscreteDomain domain) {
return ContiguousSet.create(this, domain);
}
/**
* Returns the canonical form of this range in the given domain. The canonical form has the
* following properties:
*
*
* - equivalence: {@code a.canonical().contains(v) == a.contains(v)} for all {@code v} (in other
* words, {@code a.canonical(domain).asSet(domain).equals(a.asSet(domain))}
*
- uniqueness: unless {@code a.isEmpty()}, {@code a.asSet(domain).equals(b.asSet(domain))}
* implies {@code a.canonical(domain).equals(b.canonical(domain))}
*
- idempotence: {@code a.canonical(domain).canonical(domain).equals(a.canonical(domain))}
*
*
* Furthermore, this method guarantees that the range returned will be one of the following
* canonical forms:
*
*
* - [start..end)
*
- [start..+∞)
*
- (-∞..end) (only if type {@code C} is unbounded below)
*
- (-∞..+∞) (only if type {@code C} is unbounded below)
*
*/
public Range canonical(DiscreteDomain domain) {
checkNotNull(domain);
Cut lower = lowerBound.canonical(domain);
Cut 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 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('\u2025');
upperBound.describeAsUpperBound(sb);
return sb.toString();
}
/**
* Used to avoid http://bugs.sun.com/view_bug.do?bug_id=6558557
*/
private static SortedSet cast(Iterable iterable) {
return (SortedSet) iterable;
}
@SuppressWarnings("unchecked") // this method may throw CCE
static int compareOrThrow(Comparable left, Comparable right) {
return left.compareTo(right);
}
private static final long serialVersionUID = 0;
}