compact1, compact2, compact3
java.util.function
Interface Function<T,R>
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- Type Parameters:
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T- the type of the input to the function -
R- the type of the result of the function
- All Known Subinterfaces:
- UnaryOperator<T>
- Functional Interface:
- This is a functional interface and can therefore be used as the assignment target for a lambda expression or method reference.
@FunctionalInterface public interface Function<T,R>
Represents a function that accepts one argument and produces a result.This is a functional interface whose functional method is
apply(Object).- Since:
- 1.8
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Method Summary
All Methods Static Methods Instance Methods Abstract Methods Default Methods Modifier and Type Method and Description default <V> Function<T,V>andThen(Function<? super R,? extends V> after)Returns a composed function that first applies this function to its input, and then applies theafterfunction to the result.Rapply(T t)Applies this function to the given argument.default <V> Function<V,R>compose(Function<? super V,? extends T> before)Returns a composed function that first applies thebeforefunction to its input, and then applies this function to the result.static <T> Function<T,T>identity()Returns a function that always returns its input argument.
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Method Detail
apply
R apply(T t)
Applies this function to the given argument.- Parameters:
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t- the function argument - Returns:
- the function result
compose
default <V> Function<V,R> compose(Function<? super V,? extends T> before)
Returns a composed function that first applies thebeforefunction to its input, and then applies this function to the result. If evaluation of either function throws an exception, it is relayed to the caller of the composed function.- Type Parameters:
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V- the type of input to thebeforefunction, and to the composed function - Parameters:
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before- the function to apply before this function is applied - Returns:
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a composed function that first applies the
beforefunction and then applies this function - Throws:
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NullPointerException- if before is null - See Also:
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andThen(Function)
andThen
default <V> Function<T,V> andThen(Function<? super R,? extends V> after)
Returns a composed function that first applies this function to its input, and then applies theafterfunction to the result. If evaluation of either function throws an exception, it is relayed to the caller of the composed function.- Type Parameters:
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V- the type of output of theafterfunction, and of the composed function - Parameters:
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after- the function to apply after this function is applied - Returns:
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a composed function that first applies this function and then applies the
afterfunction - Throws:
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NullPointerException- if after is null - See Also:
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compose(Function)
identity
static <T> Function<T,T> identity()
Returns a function that always returns its input argument.- Type Parameters:
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T- the type of the input and output objects to the function - Returns:
- a function that always returns its input argument
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