Package org.apache.commons.collections4

Class ClosureUtils

  • public class ClosureUtils
extends java.lang.Object
    ClosureUtils provides reference implementations and utilities for the Closure functor interface. The supplied closures are:
    • Invoker - invokes a method on the input object
    • For - repeatedly calls a closure for a fixed number of times
    • While - repeatedly calls a closure while a predicate is true
    • Chained - chains two or more closures together
    • If - calls one closure or another based on a predicate
    • Switch - calls one closure based on one or more predicates
    • SwitchMap - calls one closure looked up from a Map
    • Transformer - wraps a Transformer as a Closure
    • NOP - does nothing
    • Exception - always throws an exception

    Since v4.1 only closures which are considered to be safe are Serializable. Closures considered to be unsafe for serialization are:

    • Invoker
    • For
    • While
    Since:
    3.0

    • Method Summary

      All Methods Static Methods Concrete Methods 
      Modifier and Type Method Description
      static <E> Closure<E> asClosure​(Transformer<? super E,​?> transformer)
      Creates a Closure that calls a Transformer each time it is called.
      static <E> Closure<E> chainedClosure​(java.util.Collection<? extends Closure<? super E>> closures)
      Create a new Closure that calls each closure in turn, passing the result into the next closure.
      static <E> Closure<E> chainedClosure​(Closure<? super E>... closures)
      Create a new Closure that calls each closure in turn, passing the result into the next closure.
      static <E> Closure<E> doWhileClosure​(Closure<? super E> closure, Predicate<? super E> predicate)
      Creates a Closure that will call the closure once and then repeatedly until the predicate returns false.
      static <E> Closure<E> exceptionClosure()
      Gets a Closure that always throws an exception.
      static <E> Closure<E> forClosure​(int count, Closure<? super E> closure)
      Creates a Closure that will call the closure count times.
      static <E> Closure<E> ifClosure​(Predicate<? super E> predicate, Closure<? super E> trueClosure)
      Create a new Closure that calls another closure based on the result of the specified predicate.
      static <E> Closure<E> ifClosure​(Predicate<? super E> predicate, Closure<? super E> trueClosure, Closure<? super E> falseClosure)
      Create a new Closure that calls one of two closures depending on the specified predicate.
      static <E> Closure<E> invokerClosure​(java.lang.String methodName)
      Creates a Closure that will invoke a specific method on the closure's input object by reflection.
      static <E> Closure<E> invokerClosure​(java.lang.String methodName, java.lang.Class<?>[] paramTypes, java.lang.Object[] args)
      Creates a Closure that will invoke a specific method on the closure's input object by reflection.
      static <E> Closure<E> nopClosure()
      Gets a Closure that will do nothing.
      static <E> Closure<E> switchClosure​(java.util.Map<Predicate<E>,​Closure<E>> predicatesAndClosures)
      Create a new Closure that calls one of the closures depending on the predicates.
      static <E> Closure<E> switchClosure​(Predicate<? super E>[] predicates, Closure<? super E>[] closures)
      Create a new Closure that calls one of the closures depending on the predicates.
      static <E> Closure<E> switchClosure​(Predicate<? super E>[] predicates, Closure<? super E>[] closures, Closure<? super E> defaultClosure)
      Create a new Closure that calls one of the closures depending on the predicates.
      static <E> Closure<E> switchMapClosure​(java.util.Map<? extends E,​Closure<E>> objectsAndClosures)
      Create a new Closure that uses the input object as a key to find the closure to call.
      static <E> Closure<E> whileClosure​(Predicate<? super E> predicate, Closure<? super E> closure)
      Creates a Closure that will call the closure repeatedly until the predicate returns false.

      • Methods inherited from class java.lang.Object

        equals, getClass, hashCode, notify, notifyAll, toString, wait, wait, wait

    • Method Detail

      • exceptionClosure

        public static <E> Closure<E> exceptionClosure()
        Gets a Closure that always throws an exception. This could be useful during testing as a placeholder.
        Type Parameters:
        E - the type that the closure acts on
        Returns:
        the closure
        See Also:
        ExceptionClosure

      • nopClosure

        public static <E> Closure<E> nopClosure()
        Gets a Closure that will do nothing. This could be useful during testing as a placeholder.
        Type Parameters:
        E - the type that the closure acts on
        Returns:
        the closure
        See Also:
        NOPClosure

      • asClosure

        public static <E> Closure<E> asClosure​(Transformer<? super E,​?> transformer)
        Creates a Closure that calls a Transformer each time it is called. The transformer will be called using the closure's input object. The transformer's result will be ignored.
        Type Parameters:
        E - the type that the closure acts on
        Parameters:
        transformer - the transformer to run each time in the closure, null means nop
        Returns:
        the closure
        See Also:
        TransformerClosure

      • forClosure

        public static <E> Closure<E> forClosure​(int count,
                                        Closure<? super E> closure)
        Creates a Closure that will call the closure count times.

        A null closure or zero count returns the NOPClosure.

        Type Parameters:
        E - the type that the closure acts on
        Parameters:
        count - the number of times to loop
        closure - the closure to call repeatedly
        Returns:
        the for closure
        See Also:
        ForClosure

      • whileClosure

        public static <E> Closure<E> whileClosure​(Predicate<? super E> predicate,
                                          Closure<? super E> closure)
        Creates a Closure that will call the closure repeatedly until the predicate returns false.
        Type Parameters:
        E - the type that the closure acts on
        Parameters:
        predicate - the predicate to use as an end of loop test, not null
        closure - the closure to call repeatedly, not null
        Returns:
        the while closure
        Throws:
        java.lang.NullPointerException - if either argument is null
        See Also:
        WhileClosure

      • doWhileClosure

        public static <E> Closure<E> doWhileClosure​(Closure<? super E> closure,
                                            Predicate<? super E> predicate)
        Creates a Closure that will call the closure once and then repeatedly until the predicate returns false.
        Type Parameters:
        E - the type that the closure acts on
        Parameters:
        closure - the closure to call repeatedly, not null
        predicate - the predicate to use as an end of loop test, not null
        Returns:
        the do-while closure
        Throws:
        java.lang.NullPointerException - if either argument is null
        See Also:
        WhileClosure

      • invokerClosure

        public static <E> Closure<E> invokerClosure​(java.lang.String methodName)
        Creates a Closure that will invoke a specific method on the closure's input object by reflection.
        Type Parameters:
        E - the type that the closure acts on
        Parameters:
        methodName - the name of the method
        Returns:
        the invoker closure
        Throws:
        java.lang.NullPointerException - if the method name is null
        See Also:
        InvokerTransformer, TransformerClosure

      • invokerClosure

        public static <E> Closure<E> invokerClosure​(java.lang.String methodName,
                                            java.lang.Class<?>[] paramTypes,
                                            java.lang.Object[] args)
        Creates a Closure that will invoke a specific method on the closure's input object by reflection.
        Type Parameters:
        E - the type that the closure acts on
        Parameters:
        methodName - the name of the method
        paramTypes - the parameter types
        args - the arguments
        Returns:
        the invoker closure
        Throws:
        java.lang.NullPointerException - if the method name is null
        java.lang.IllegalArgumentException - if the paramTypes and args don't match
        See Also:
        InvokerTransformer, TransformerClosure

      • chainedClosure

        public static <E> Closure<E> chainedClosure​(Closure<? super E>... closures)
        Create a new Closure that calls each closure in turn, passing the result into the next closure.
        Type Parameters:
        E - the type that the closure acts on
        Parameters:
        closures - an array of closures to chain
        Returns:
        the chained closure
        Throws:
        java.lang.NullPointerException - if the closures array is null
        java.lang.NullPointerException - if any closure in the array is null
        See Also:
        ChainedClosure

      • chainedClosure

        public static <E> Closure<E> chainedClosure​(java.util.Collection<? extends Closure<? super E>> closures)
        Create a new Closure that calls each closure in turn, passing the result into the next closure. The ordering is that of the iterator() method on the collection.
        Type Parameters:
        E - the type that the closure acts on
        Parameters:
        closures - a collection of closures to chain
        Returns:
        the chained closure
        Throws:
        java.lang.NullPointerException - if the closures collection is null
        java.lang.NullPointerException - if any closure in the collection is null
        java.lang.IllegalArgumentException - if the closures collection is empty
        See Also:
        ChainedClosure

      • ifClosure

        public static <E> Closure<E> ifClosure​(Predicate<? super E> predicate,
                                       Closure<? super E> trueClosure)
        Create a new Closure that calls another closure based on the result of the specified predicate.
        Type Parameters:
        E - the type that the closure acts on
        Parameters:
        predicate - the validating predicate
        trueClosure - the closure called if the predicate is true
        Returns:
        the if closure
        Throws:
        java.lang.NullPointerException - if the predicate or closure is null
        Since:
        3.2
        See Also:
        IfClosure

      • ifClosure

        public static <E> Closure<E> ifClosure​(Predicate<? super E> predicate,
                                       Closure<? super E> trueClosure,
                                       Closure<? super E> falseClosure)
        Create a new Closure that calls one of two closures depending on the specified predicate.
        Type Parameters:
        E - the type that the closure acts on
        Parameters:
        predicate - the predicate to switch on
        trueClosure - the closure called if the predicate is true
        falseClosure - the closure called if the predicate is false
        Returns:
        the switch closure
        Throws:
        java.lang.NullPointerException - if the predicate or either closure is null
        See Also:
        IfClosure

      • switchClosure

        public static <E> Closure<E> switchClosure​(Predicate<? super E>[] predicates,
                                           Closure<? super E>[] closures)
        Create a new Closure that calls one of the closures depending on the predicates.

        The closure at array location 0 is called if the predicate at array location 0 returned true. Each predicate is evaluated until one returns true.

        Type Parameters:
        E - the type that the closure acts on
        Parameters:
        predicates - an array of predicates to check, not null
        closures - an array of closures to call, not null
        Returns:
        the switch closure
        Throws:
        java.lang.NullPointerException - if the either array is null
        java.lang.NullPointerException - if any element in the arrays is null
        java.lang.IllegalArgumentException - if the arrays have different sizes
        See Also:
        SwitchClosure

      • switchClosure

        public static <E> Closure<E> switchClosure​(Predicate<? super E>[] predicates,
                                           Closure<? super E>[] closures,
                                           Closure<? super E> defaultClosure)
        Create a new Closure that calls one of the closures depending on the predicates.

        The closure at array location 0 is called if the predicate at array location 0 returned true. Each predicate is evaluated until one returns true. If no predicates evaluate to true, the default closure is called.

        Type Parameters:
        E - the type that the closure acts on
        Parameters:
        predicates - an array of predicates to check, not null
        closures - an array of closures to call, not null
        defaultClosure - the default to call if no predicate matches
        Returns:
        the switch closure
        Throws:
        java.lang.NullPointerException - if the either array is null
        java.lang.NullPointerException - if any element in the arrays is null
        java.lang.IllegalArgumentException - if the arrays are different sizes
        See Also:
        SwitchClosure

      • switchClosure

        public static <E> Closure<E> switchClosure​(java.util.Map<Predicate<E>,​Closure<E>> predicatesAndClosures)
        Create a new Closure that calls one of the closures depending on the predicates.

        The Map consists of Predicate keys and Closure values. A closure is called if its matching predicate returns true. Each predicate is evaluated until one returns true. If no predicates evaluate to true, the default closure is called. The default closure is set in the map with a null key. The ordering is that of the iterator() method on the entryset collection of the map.

        Type Parameters:
        E - the type that the closure acts on
        Parameters:
        predicatesAndClosures - a map of predicates to closures
        Returns:
        the switch closure
        Throws:
        java.lang.NullPointerException - if the map is null
        java.lang.NullPointerException - if any closure in the map is null
        java.lang.IllegalArgumentException - if the map is empty
        java.lang.ClassCastException - if the map elements are of the wrong type
        See Also:
        SwitchClosure

      • switchMapClosure

        public static <E> Closure<E> switchMapClosure​(java.util.Map<? extends E,​Closure<E>> objectsAndClosures)
        Create a new Closure that uses the input object as a key to find the closure to call.

        The Map consists of object keys and Closure values. A closure is called if the input object equals the key. If there is no match, the default closure is called. The default closure is set in the map using a null key.

        Type Parameters:
        E - the type that the closure acts on
        Parameters:
        objectsAndClosures - a map of objects to closures
        Returns:
        the closure
        Throws:
        java.lang.NullPointerException - if the map is null
        java.lang.NullPointerException - if any closure in the map is null
        java.lang.IllegalArgumentException - if the map is empty
        See Also:
        SwitchClosure