com.google.common.collect
Class Range<C extends Comparable>

java.lang.Object
  com.google.common.collect.Range<C>

All Implemented Interfaces:

Predicate<C>, Serializable

@GwtCompatible
@Beta
public final class Range<C extends Comparable>
extends Object
implements Predicate<C>, Serializable

A range, sometimes known as an interval, is a convex (informally, "contiguous" or "unbroken") portion of a particular domain. Formally, convexity means that for any a <= b <= c, range.contains(a) && range.contains(c) implies that range.contains(b).

A range is characterized by its lower and upper bounds (extremes), each of which can open (exclusive of its endpoint), closed (inclusive of its endpoint), or unbounded. This yields nine basic types of ranges:

• (a..b) = {x | a < x < b}
• [a..b] = {x | a <= x <= b}
• [a..b) = {x | a <= x < b}
• (a..b] = {x | a < x <= b}
• (a..+∞) = {x | x > a}
• [a..+∞) = {x | x >= a}
• (-∞..b) = {x | x < b}
• (-∞..b] = {x | x <= b}
• (-∞..+∞) = all values

(The notation {x | statement} is read "the set of all x such that statement.")

Notice that we use a square bracket ([ ]) to denote that an range is closed on that end, and a parenthesis (( )) when it is open or unbounded.

The values a and b used above are called endpoints. The upper endpoint may not be less than the lower endpoint. The endpoints may be equal only if at least one of the bounds is closed:

• [a..a] : singleton range
• [a..a); (a..a] : empty, but valid
• (a..a) : invalid

Instances of this type can be obtained using the static factory methods in the Ranges class.

Instances of Range are immutable. It is strongly encouraged to use this class only with immutable data types. When creating a range over a mutable type, take great care not to allow the value objects to mutate after the range is created.

In this and other range-related specifications, concepts like "equal", "same", "unique" and so on are based on Comparable.compareTo(T) returning zero, not on Object.equals(java.lang.Object) returning true. Of course, when these methods are kept consistent (as defined in Comparable), this is not an issue.

A range a is said to be the maximal range having property P if, for all ranges b also having property P, a.encloses(b). Likewise, a is minimal when b.encloses(a) for all b having property P. See, for example, the definition of intersection(com.google.common.collect.Range).

This class can be used with any type which implements Comparable; it does not require Comparable<? super C> because this would be incompatible with pre-Java 5 types. If this class is used with a perverse Comparable type (Foo implements Comparable<Bar> where Bar is not a supertype of Foo), any of its methods may throw ClassCastException. (There is no good reason for such a type to exist.)

When evaluated as a Predicate, a range yields the same result as invoking contains(C).

Since:

10.0

Author:

Kevin Bourrillion, Gregory Kick

See Also:

Serialized Form

Method Summary

boolean	apply(C input) Equivalent to contains(C); provided only to satisfy the Predicate interface.
ContiguousSet<C>	asSet(DiscreteDomain<C> domain) Returns an ImmutableSortedSet containing the same values in the given domain contained by this range.
Range<C>	canonical(DiscreteDomain<C> domain) Returns the canonical form of this range in the given domain.
boolean	contains(C value) Returns true if value is within the bounds of this range.
boolean	containsAll(Iterable<? extends C> values) Returns true if every element in values is contained in this range.
boolean	encloses(Range<C> other) Returns true if the bounds of other do not extend outside the bounds of this range.
boolean	equals(Object object) Returns true if object is a range having the same endpoints and bound types as this range.
int	hashCode() Returns a hash code for this range.
boolean	hasLowerBound() Returns true if this range has a lower endpoint.
boolean	hasUpperBound() Returns true if this range has an upper endpoint.
Range<C>	intersection(Range<C> other) Returns the maximal range enclosed by both this range and other, if such a range exists.
boolean	isConnected(Range<C> other) Returns true if there exists a (possibly empty) range which is enclosed by both this range and other.
boolean	isEmpty() Returns true if this range is of the form [v..v) or (v..v].
BoundType	lowerBoundType() Returns the type of this range's lower bound: BoundType.CLOSED if the range includes its lower endpoint, BoundType.OPEN if it does not.
C	lowerEndpoint() Returns the lower endpoint of this range.
Range<C>	span(Range<C> other) Returns the minimal range that encloses both this range and other.
String	toString() Returns a string representation of this range, such as "[3..5)" (other examples are listed in the class documentation).
BoundType	upperBoundType() Returns the type of this range's upper bound: BoundType.CLOSED if the range includes its upper endpoint, BoundType.OPEN if it does not.
C	upperEndpoint() Returns the upper endpoint of this range.

Methods inherited from class java.lang.Object

clone, finalize, getClass, notify, notifyAll, wait, wait, wait

Method Detail

hasLowerBound

public boolean hasLowerBound()

Returns true if this range has a lower endpoint.

lowerEndpoint

public C lowerEndpoint()

Returns the lower endpoint of this range.

Throws:

IllegalStateException - if this range is unbounded below (that is, hasLowerBound() returns false)

lowerBoundType

public BoundType lowerBoundType()

Returns the type of this range's lower bound: BoundType.CLOSED if the range includes its lower endpoint, BoundType.OPEN if it does not.

Throws:

IllegalStateException - if this range is unbounded below (that is, hasLowerBound() returns false)

hasUpperBound

public boolean hasUpperBound()

Returns true if this range has an upper endpoint.

upperEndpoint

public C upperEndpoint()

Returns the upper endpoint of this range.

Throws:

IllegalStateException - if this range is unbounded above (that is, hasUpperBound() returns false)

upperBoundType

public BoundType upperBoundType()

Returns the type of this range's upper bound: BoundType.CLOSED if the range includes its upper endpoint, BoundType.OPEN if it does not.

Throws:

IllegalStateException - if this range is unbounded above (that is, hasUpperBound() returns false)

isEmpty

public boolean isEmpty()

Returns true if this range is of the form [v..v) or (v..v]. (This does not encompass ranges of the form (v..v), because such ranges are invalid and can't be constructed at all.)

Note that certain discrete ranges such as the integer range (3..4) are not considered empty, even though they contain no actual values.

contains

public boolean contains(C value)

Returns true if value is within the bounds of this range. For example, on the range [0..2), contains(1) returns true, while contains(2) returns false.

apply

public boolean apply(C input)

Equivalent to contains(C); provided only to satisfy the Predicate interface. When using a reference of type Range, always invoke contains(C) directly instead.

Specified by:

apply in interface Predicate<C extends Comparable>

containsAll

public boolean containsAll(Iterable<? extends C> values)

Returns true if every element in values is contained in this range.

encloses

public boolean encloses(Range<C> other)

Returns true if the bounds of other do not extend outside the bounds of this range. Examples:

• [3..6] encloses [4..5]
• (3..6) encloses (3..6)
• [3..6] encloses [4..4) (even though the latter is empty)
• (3..6] does not enclose [3..6]
• [4..5] does not enclose (3..6) (even though it contains every value contained by the latter range)
• [3..6] does not enclose (1..1] (even though it contains every value contained by the latter range)

Note that if a.encloses(b), then b.contains(v) implies a.contains(v), but as the last two examples illustrate, the converse is not always true.

The encloses relation has the following properties:

• reflexive: a.encloses(a) is always true
• antisymmetric: a.encloses(b) && b.encloses(a) implies a.equals(b)
• transitive: a.encloses(b) && b.encloses(c) implies a.encloses(c)
• not a total ordering: !a.encloses(b) does not imply b.encloses(a)
• there exists a maximal range, for which encloses is always true
• there also exist minimal ranges, for which encloses(b) is always false when !equals(b)
• if a.encloses(b), then a.isConnected(b) is true.

intersection

public Range<C> intersection(Range<C> other)

Returns the maximal range enclosed by both this range and other, if such a range exists.

For example, the intersection of [1..5] and (3..7) is (3..5]. The resulting range may be empty; for example, [1..5) intersected with [5..7) yields the empty range [5..5).

Generally, the intersection exists if and only if this range and other are connected.

The intersection operation has the following properties:

• commutative: a.intersection(b) produces the same result as b.intersection(a)
• associative: a.intersection(b).intersection(c) produces the same result as a.intersection(b.intersection(c))
• idempotent: a.intersection(a) equals a
• identity (Ranges.all()): a.intersection(Ranges.all()) equals a

Throws:

IllegalArgumentException - if no range exists that is enclosed by both these ranges

isConnected

public boolean isConnected(Range<C> other)

Returns true if there exists a (possibly empty) range which is enclosed by both this range and other.

For example,

• [2, 4) and [5, 7) are not connected
• [2, 4) and [3, 5) are connected, because both enclose [3, 4)
• [2, 4) and [4, 6) are connected, because both enclose the empty range [4, 4)

Note that this range and other have a well-defined union and intersection (as a single, possibly-empty range) if and only if this method returns true.

The connectedness relation has the following properties:

• symmetric: a.isConnected(b) produces the same result as b.isConnected(a)
• reflexive: a.isConnected(a) returns true

span

public Range<C> span(Range<C> other)

Returns the minimal range that encloses both this range and other. For example, the span of [1..3] and (5..7) is [1..7). Note that the span may contain values that are not contained by either original range.

The span operation has the following properties:

• closed: the range a.span(b) exists for all ranges a and b
• commutative: a.span(b) equals b.span(a)
• associative: a.span(b).span(c) equals a.span(b.span(c))
• idempotent: a.span(a) equals a

Note that the returned range is also called the union of this range and other if and only if the ranges are connected.

asSet

@GwtCompatible(serializable=false)
public ContiguousSet<C> asSet(DiscreteDomain<C> domain)

Returns an ImmutableSortedSet containing the same values in the given domain contained by this range.

Note: a.asSet().equals(b.asSet()) does not imply a.equals(b)! For example, a and b could be [2..4] and (1..5), or the empty ranges [3..3) and [4..4).

Warning: Be extremely careful what you do with the asSet view of a large range (such as Ranges.greaterThan(0)). Certain operations on such a set can be performed efficiently, but others (such as Set.hashCode() or Collections.frequency(java.util.Collection, java.lang.Object)) can cause major performance problems.

The returned set's Object.toString() method returns a short-hand form of set's contents such as "[1..100]"}.

Throws:

IllegalArgumentException - if neither this range nor the domain has a lower bound, or if neither has an upper bound

canonical

public Range<C> canonical(DiscreteDomain<C> domain)

Returns the canonical form of this range in the given domain. The canonical form has the following properties:

• equivalence: a.canonical().contains(v) == a.contains(v) for all v (in other words, a.canonical(domain).asSet(domain).equals(a.asSet(domain))
• uniqueness: unless a.isEmpty(), a.asSet(domain).equals(b.asSet(domain)) implies a.canonical(domain).equals(b.canonical(domain))
• idempotence: 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 C is unbounded below)
• (-∞..+∞) (only if type C is unbounded below)

equals

public boolean equals(@Nullable
                      Object object)

Returns true if object is a range having the same endpoints and bound types as this range. Note that discrete ranges such as (1..4) and [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 [3..3), (3..3], (4..4] are all unequal.

Specified by:

equals in interface Predicate<C extends Comparable>

Overrides:

equals in class Object

hashCode

public int hashCode()

Returns a hash code for this range.

Overrides:

hashCode in class Object

toString

public String toString()

Returns a string representation of this range, such as "[3..5)" (other examples are listed in the class documentation).

Overrides:

toString in class Object