Range (Guava: Google Core Libraries for Java 13.0-rc2 API)

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

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

All Implemented Interfaces:: Predicate<C>, Serializable

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

A range (or "interval") defines the boundaries around a contiguous span of values of some 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 DiscreteDomain can be provided to the 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 ([ ]) indicates that the range is closed on that side; a parenthesis (( )) means it is either open or unbounded. The construct {x | statement} is read "the set of all x such that statement.")

Notation Definition Factory method
(a..b) {x | a < x < b} open
[a..b] {x | a <= x <= b} closed
(a..b] {x | a < x <= b} openClosed
[a..b) {x | a <= x < b} closedOpen
(a..+∞) {x | x > a} greaterThan
[a..+∞) {x | x >= a} atLeast
(-∞..b) {x | x < b} lessThan
(-∞..b] {x | x <= b} atMost
(-∞..+∞) {x} 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:

[a..a] : a singleton range
[a..a); (a..a] : empty ranges; also valid
(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 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 compareTo returns zero, not whether equals returns true.
A class which implements Comparable<UnrelatedType> is very broken, and will cause undefined horrible things to happen in 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 Ranges class.
Ranges are convex: whenever two values are contained, all values in between them must also be contained. More formally, for any c1 <= c2 <= c3 of type C, r.contains(c1) && r.contains(c3) implies r.contains(c2)). This means that a Range<Integer> can never be used to represent, say, "all prime numbers from 1 to 100."
When evaluated as a Predicate, a range yields the same result as invoking contains(C).
Terminology note: 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.

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 `ContiguousSet` 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> connectedRange)` Returns the maximal range enclosed by both this range and `connectedRange`, 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`

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.

Being reflexive, antisymmetric and transitive, the encloses relation defines a partial order over ranges. There exists a unique maximal range according to this relation, and also numerous minimal ranges. Enclosure also implies connectedness.

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 is both reflexive and symmetric, but does not form an equivalence relation as it is not transitive.

intersection

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

Returns the maximal range enclosed by both this range and connectedRange, 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).

The intersection exists if and only if the two ranges are connected.

The intersection operation is commutative, associative and idempotent, and its identity element is Ranges.all()).

Throws:: IllegalArgumentException - if isConnected(connectedRange) is false

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).

If the input ranges are 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 intersection, this operation is commutative, associative and idempotent. Unlike it, it is always well-defined for any two input ranges.

asSet

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

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

Note: a.asSet(d).equals(b.asSet(d)) 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 the 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