Package com.google.gerrit.index.query

Class Predicate<T>

java.lang.Object

com.google.gerrit.index.query.Predicate<T>

Type Parameters:

T - type of object the predicate can evaluate in memory.

Direct Known Subclasses:

AndPredicate, IndexedQuery, NotPredicate, OperatorPredicate, OrPredicate

public abstract class Predicate<T>
extends Object

An abstract predicate tree for any form of query.

Implementations should be immutable, such that the meaning of a predicate never changes once constructed. They should ensure their immutable promise by defensively copying any structures which might be modified externally, but was passed into the object's constructor.

However, implementations may retain non-thread-safe caches internally, to speed up evaluation operations within the context of one thread's evaluation of the predicate. As a result, callers should assume predicates are not thread-safe, but that two predicate graphs produce the same results given the same inputs if they are equals(Object).

Predicates should support deep inspection whenever possible, so that generic algorithms can be written to operate against them. Predicates which contain other predicates should override getChildren() to return the list of children nested within the predicate.

Constructor Summary

Constructors

Constructor	Description
Predicate()

Method Summary

Modifier and Type	Method	Description
static <T> Predicate<T>	and(Predicate<T>... that)	Combine the passed predicates into a single AND node.
static <T> Predicate<T>	and(Collection<? extends Predicate<T>> that)	Combine the passed predicates into a single AND node.
static <T> Predicate<T>	any()	A predicate that matches any input, always, with no cost.
Matchable<T>	asMatchable()
abstract Predicate<T>	copy(Collection<? extends Predicate<T>> children)	Create a copy of this predicate, with new children.
abstract boolean	equals(Object other)
int	estimateCost()
Predicate<T>	getChild(int i)	Same as getChildren().get(i)
int	getChildCount()	Same as getChildren().size()
List<Predicate<T>>	getChildren()	Get the children of this predicate, if any.
int	getLeafCount()	Get the number of leaf terms in this predicate.
abstract int	hashCode()
boolean	isMatchable()
static <T> Predicate<T>	not(Predicate<T> that)	Invert the passed node.
static <T> Predicate<T>	or(Predicate<T>... that)	Combine the passed predicates into a single OR node.
static <T> Predicate<T>	or(Collection<? extends Predicate<T>> that)	Combine the passed predicates into a single OR node.

Methods inherited from class java.lang.Object

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

Constructor Detail

Predicate

public Predicate()

Method Detail

any

public static <T> Predicate<T> any()

A predicate that matches any input, always, with no cost.

and

@SafeVarargs
public static <T> Predicate<T> and(Predicate<T>... that)

Combine the passed predicates into a single AND node.

and

public static <T> Predicate<T> and(Collection<? extends Predicate<T>> that)

Combine the passed predicates into a single AND node.

or

@SafeVarargs
public static <T> Predicate<T> or(Predicate<T>... that)

Combine the passed predicates into a single OR node.

or

public static <T> Predicate<T> or(Collection<? extends Predicate<T>> that)

Combine the passed predicates into a single OR node.

not

public static <T> Predicate<T> not(Predicate<T> that)

Invert the passed node.

getChildren

public List<Predicate<T>> getChildren()

Get the children of this predicate, if any.

getChildCount

public int getChildCount()

Same as getChildren().size()

getChild

public Predicate<T> getChild(int i)

Same as getChildren().get(i)

getLeafCount

public int getLeafCount()

Get the number of leaf terms in this predicate.

copy

public abstract Predicate<T> copy(Collection<? extends Predicate<T>> children)

Create a copy of this predicate, with new children.

isMatchable

public boolean isMatchable()

asMatchable

public Matchable<T> asMatchable()

estimateCost

public int estimateCost()

Returns:

a cost estimate to run this predicate, higher figures cost more.

hashCode

public abstract int hashCode()

Overrides:

hashCode in class Object

equals

public abstract boolean equals(Object other)

Overrides:

equals in class Object