Functional interfaces have a single functionality to exhibit. For example, a Comparable interface with a single method ‘compareTo’ is used for comparison purpose. Java 8 has defined a lot of functional interfaces to be used extensively in lambda expressions. Following is the list of functional interfaces defined in java.util.Function package.
| S. No. | Interface & Description |
|---|---|
| 1 | BiConsumer<T,U>
Represents an operation that accepts two input arguments, and returns no result.
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| 2 | BiFunction<T,U,R>
Represents a function that accepts two arguments and produces a result.
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| 3 | BinaryOperator<T>
Represents an operation upon two operands of the same type, producing a result of the same type as the operands.
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| 4 | BiPredicate<T,U>
Represents a predicate (Boolean-valued function) of two arguments.
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| 5 | BooleanSupplier
Represents a supplier of Boolean-valued results.
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| 6 | Consumer<T>
Represents an operation that accepts a single input argument and returns no result.
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| 7 | DoubleBinaryOperator
Represents an operation upon two double-valued operands and producing a double-valued result.
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| 8 | DoubleConsumer
Represents an operation that accepts a single double-valued argument and returns no result.
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| 9 | DoubleFunction<R>
Represents a function that accepts a double-valued argument and produces a result.
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| 10 | DoublePredicate
Represents a predicate (Boolean-valued function) of one double-valued argument.
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| 11 | DoubleSupplier
Represents a supplier of double-valued results.
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| 12 | DoubleToIntFunction
Represents a function that accepts a double-valued argument and produces an int-valued result.
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| 13 | DoubleToLongFunction
Represents a function that accepts a double-valued argument and produces a long-valued result.
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| 14 | DoubleUnaryOperator
Represents an operation on a single double-valued operand that produces a double-valued result.
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| 15 | Function<T,R>
Represents a function that accepts one argument and produces a result.
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| 16 | IntBinaryOperator
Represents an operation upon two int-valued operands and produces an int-valued result.
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| 17 | IntConsumer
Represents an operation that accepts a single int-valued argument and returns no result.
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| 18 | IntFunction<R>
Represents a function that accepts an int-valued argument and produces a result.
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| 19 | IntPredicate
Represents a predicate (Boolean-valued function) of one int-valued argument.
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| 20 | IntSupplier
Represents a supplier of int-valued results.
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| 21 | IntToDoubleFunction
Represents a function that accepts an int-valued argument and produces a double-valued result.
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| 22 | IntToLongFunction
Represents a function that accepts an int-valued argument and produces a long-valued result.
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| 23 | IntUnaryOperator
Represents an operation on a single int-valued operand that produces an int-valued result.
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| 24 | LongBinaryOperator
Represents an operation upon two long-valued operands and produces a long-valued result.
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| 25 | LongConsumer
Represents an operation that accepts a single long-valued argument and returns no result.
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| 26 | LongFunction<R>
Represents a function that accepts a long-valued argument and produces a result.
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| 27 | LongPredicate
Represents a predicate (Boolean-valued function) of one long-valued argument.
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| 28 | LongSupplier
Represents a supplier of long-valued results.
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| 29 | LongToDoubleFunction
Represents a function that accepts a long-valued argument and produces a double-valued result.
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| 30 | LongToIntFunction
Represents a function that accepts a long-valued argument and produces an int-valued result.
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| 31 | LongUnaryOperator
Represents an operation on a single long-valued operand that produces a long-valued result.
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| 32 | ObjDoubleConsumer<T>
Represents an operation that accepts an object-valued and a double-valued argument, and returns no result.
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| 33 | ObjIntConsumer<T>
Represents an operation that accepts an object-valued and an int-valued argument, and returns no result.
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| 34 | ObjLongConsumer<T>
Represents an operation that accepts an object-valued and a long-valued argument, and returns no result.
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| 35 | Predicate<T>
Represents a predicate (Boolean-valued function) of one argument.
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| 36 | Supplier<T>
Represents a supplier of results.
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| 37 | ToDoubleBiFunction<T,U>
Represents a function that accepts two arguments and produces a double-valued result.
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| 38 | ToDoubleFunction<T>
Represents a function that produces a double-valued result.
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| 39 | ToIntBiFunction<T,U>
Represents a function that accepts two arguments and produces an int-valued result.
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| 40 | ToIntFunction<T>
Represents a function that produces an int-valued result.
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| 41 | ToLongBiFunction<T,U>
Represents a function that accepts two arguments and produces a long-valued result.
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| 42 | ToLongFunction<T>
Represents a function that produces a long-valued result.
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| 43 | UnaryOperator<T>
Represents an operation on a single operand that produces a result of the same type as its operand.
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