Java 8 – Functional Interfaces

Java 8 – Functional Interfaces

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
1BiConsumer<T,U>Represents an operation that accepts two input arguments, and returns no result.
2BiFunction<T,U,R>Represents a function that accepts two arguments and produces a result.
3BinaryOperator<T>Represents an operation upon two operands of the same type, producing a result of the same type as the operands.
4BiPredicate<T,U>Represents a predicate (Boolean-valued function) of two arguments.
5BooleanSupplierRepresents a supplier of Boolean-valued results.
6Consumer<T>Represents an operation that accepts a single input argument and returns no result.
7DoubleBinaryOperatorRepresents an operation upon two double-valued operands and producing a double-valued result.
8DoubleConsumerRepresents an operation that accepts a single double-valued argument and returns no result.
9DoubleFunction<R>Represents a function that accepts a double-valued argument and produces a result.
10DoublePredicateRepresents a predicate (Boolean-valued function) of one double-valued argument.
11DoubleSupplierRepresents a supplier of double-valued results.
12DoubleToIntFunctionRepresents a function that accepts a double-valued argument and produces an int-valued result.
13DoubleToLongFunctionRepresents a function that accepts a double-valued argument and produces a long-valued result.
14DoubleUnaryOperatorRepresents an operation on a single double-valued operand that produces a double-valued result.
15Function<T,R>Represents a function that accepts one argument and produces a result.
16IntBinaryOperatorRepresents an operation upon two int-valued operands and produces an int-valued result.
17IntConsumerRepresents an operation that accepts a single int-valued argument and returns no result.
18IntFunction<R>Represents a function that accepts an int-valued argument and produces a result.
19IntPredicateRepresents a predicate (Boolean-valued function) of one int-valued argument.
20IntSupplierRepresents a supplier of int-valued results.
21IntToDoubleFunctionRepresents a function that accepts an int-valued argument and produces a double-valued result.
22IntToLongFunctionRepresents a function that accepts an int-valued argument and produces a long-valued result.
23IntUnaryOperatorRepresents an operation on a single int-valued operand that produces an int-valued result.
24LongBinaryOperatorRepresents an operation upon two long-valued operands and produces a long-valued result.
25LongConsumerRepresents an operation that accepts a single long-valued argument and returns no result.
26LongFunction<R>Represents a function that accepts a long-valued argument and produces a result.
27LongPredicateRepresents a predicate (Boolean-valued function) of one long-valued argument.
28LongSupplierRepresents a supplier of long-valued results.
29LongToDoubleFunctionRepresents a function that accepts a long-valued argument and produces a double-valued result.
30LongToIntFunctionRepresents a function that accepts a long-valued argument and produces an int-valued result.
31LongUnaryOperatorRepresents an operation on a single long-valued operand that produces a long-valued result.
32ObjDoubleConsumer<T>Represents an operation that accepts an object-valued and a double-valued argument, and returns no result.
33ObjIntConsumer<T>Represents an operation that accepts an object-valued and an int-valued argument, and returns no result.
34ObjLongConsumer<T>Represents an operation that accepts an object-valued and a long-valued argument, and returns no result.
35Predicate<T>Represents a predicate (Boolean-valued function) of one argument.
36Supplier<T>Represents a supplier of results.
37ToDoubleBiFunction<T,U>Represents a function that accepts two arguments and produces a double-valued result.
38ToDoubleFunction<T>Represents a function that produces a double-valued result.
39ToIntBiFunction<T,U>Represents a function that accepts two arguments and produces an int-valued result.
40ToIntFunction<T>Represents a function that produces an int-valued result.
41ToLongBiFunction<T,U>Represents a function that accepts two arguments and produces a long-valued result.
42ToLongFunction<T>Represents a function that produces a long-valued result.
43UnaryOperator<T>Represents an operation on a single operand that produces a result of the same type as its operand.

Functional Interface Example

Predicate <T> interface is a functional interface with a method test(Object) to return a Boolean value. This interface signifies that an object is tested to be true or false.

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