Java 8 Functional Interfaces

Java 8 has many functional interfaces as defined in the Javadoc. In this blog, I'm going to explain few important Java 8 functional interfaces.

• Consumer<T>
• Arguments: T
• Returns: Void
• Supplier<T>
• Arguments: None
• Returns: T
• Function<T, R>
• Arguments: T
• Returns: R
• Predicate<T>
• Arguments: T
• Returns: boolean
• UnaryOperator<T>
• Arguments: T
• Returns: T
• BinaryOperator<T>
• Arguments: (T, T)
• Returns: T

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public class Java8 {     public static void main(String[] args) {         System.out.print("Consumer: ");         Consumer<String> consumer = (s) -> {             System.out.println(s);         };         consumer.accept("hello");           System.out.print("Supplier: ");         Supplier<String> supplier = () -> {             return "foo";         };         System.out.println(supplier.get());                   System.out.print("Function: ");         Function<Integer, String> function = (i) -> {             return "func" + i;         };         System.out.println(function.apply(1));                   System.out.print("Predicate: ");         Predicate<Integer> predicate = (i) -> {             return i == 0;         };         System.out.println(predicate.test(0));                   System.out.print("UnaryOperator: ");         UnaryOperator<Integer> unaryOperator = (i) -> {             return i * 100;         };         System.out.println(unaryOperator.apply(2));                   System.out.print("BinaryOperator: ");         BinaryOperator<Integer> binaryOperator = (i, j) -> {             return i + j;         };         System.out.println(binaryOperator.apply(3, 5));     } }

Output:

Consumer: hello
Supplier: foo
Function: func1
Predicate: true
UnaryOperator: 200
BinaryOperator: 8