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FUNCTIONAL INTERFACE IN JAVA
MASTER FUNCTIONAL PROGRAMMING FUNCTIONAL INTERFACE IN JAVA
WHAT IS FUNCTIONAL INTERFACE ?
A
Functional Interface
is an interface with exactly
one abstract method
. It’s used for
lambda expressions
and
method references
in Java 8 and later.
WHY USE FUNCTIONAL INTERFACES ?
✅ Enables functional programming in Java
✅ Reduces boilerplate code
✅ Supports clean, readable lambda expressions
KEY RULES OF FUNCTIONAL INTERFACES
– Only
one abstract method
– Can have
default
and
static
methods
– Annotated with @FunctionalInterface (optional but recommended)
COMMON BUILT-IN FUNCTIONAL INTERFACES
– Runnable
– Callable
– Comparator<T>
– Function<T, R>
– Predicate<T>
– Consumer<T>
EXAMPLE OF A FUNCTIONAL INTERFACES
@FunctionalInterface
interface MyInterface {
void sayHello();
}
MyInterface mi = () -> System.out.println("Hello!");
mi.sayHello();
FUNCTIONAL INTERFACE WITH PARAMETER
@FunctionalInterface
interface Adder {
int add(int a, int b);
}
//lambda
Adder sum = (a, b) -> a + b;
System.out.println(sum.add(5, 3));
WHY IT MATTERS IN JAVA 8
Functional Interfaces are the
foundation of Java 8’s lambda expressions
and the
Stream API
, making your code more functional, concise, and expressive.
🔗 Learn more at:
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