Lambda Expression

title: Lambda Expression in Java 8 description: Lambda expressions ka complete guide

Anonymous function — naam ke bina function. Code concise hota hai.

Syntax

java exampleWoHoTech

// (parameters) -> expression
// (parameters) -> { statements }

// Bina parameter
() -> System.out.println("Hello")

// Ek parameter (parentheses optional)
x -> x * x
(x) -> x * x

// Multiple parameters
(a, b) -> a + b

// Multiple statements
(a, b) -> {
    int sum = a + b;
    return sum;
}

Functional Interface ke saath

Lambda sirf functional interface mein use hota hai (exactly 1 abstract method).

java exampleWoHoTech

// Runnable
Runnable r = () -> System.out.println("Running!");
new Thread(r).start();

// Comparator
List<String> names = Arrays.asList("Zara", "Alex", "Mia");
names.sort((a, b) -> a.compareTo(b));
names.sort((a, b) -> a.length() - b.length()); // by length

// Custom Functional Interface
@FunctionalInterface
interface MathOperation {
    int operate(int a, int b);
}

MathOperation add = (a, b) -> a + b;
MathOperation multiply = (a, b) -> a * b;

System.out.println(add.operate(5, 3));      // 8
System.out.println(multiply.operate(5, 3)); // 15

Built-in Functional Interfaces (java.util.function)

java exampleWoHoTech

// Predicate<T> — condition check (returns boolean)
Predicate<Integer> isEven = n -> n % 2 == 0;
isEven.test(4); // true

// Function<T, R> — T input, R output
Function<String, Integer> length = s -> s.length();
length.apply("Hello"); // 5

// Consumer<T> — input, no output
Consumer<String> printer = s -> System.out.println(s);
printer.accept("Hello");

// Supplier<T> — no input, T output
Supplier<Double> random = () -> Math.random();
random.get(); // 0.XYZ

// BiFunction<T, U, R>
BiFunction<Integer, Integer, Integer> add = (a, b) -> a + b;
add.apply(3, 4); // 7

// UnaryOperator<T>
UnaryOperator<String> upper = s -> s.toUpperCase();
upper.apply("hello"); // "HELLO"

// BinaryOperator<T>
BinaryOperator<Integer> max = (a, b) -> a > b ? a : b;
max.apply(5, 3); // 5

title: Lambda Expression in Java 8 description: Lambda expressions ka complete guide

Anonymous function — naam ke bina function. Code concise hota hai.

Syntax

java exampleWoHoTech

// (parameters) -> expression
// (parameters) -> { statements }

// Bina parameter
() -> System.out.println("Hello")

// Ek parameter (parentheses optional)
x -> x * x
(x) -> x * x

// Multiple parameters
(a, b) -> a + b

// Multiple statements
(a, b) -> {
    int sum = a + b;
    return sum;
}

Functional Interface ke saath

Lambda sirf functional interface mein use hota hai (exactly 1 abstract method).

java exampleWoHoTech

// Runnable
Runnable r = () -> System.out.println("Running!");
new Thread(r).start();

// Comparator
List<String> names = Arrays.asList("Zara", "Alex", "Mia");
names.sort((a, b) -> a.compareTo(b));
names.sort((a, b) -> a.length() - b.length()); // by length

// Custom Functional Interface
@FunctionalInterface
interface MathOperation {
    int operate(int a, int b);
}

MathOperation add = (a, b) -> a + b;
MathOperation multiply = (a, b) -> a * b;

System.out.println(add.operate(5, 3));      // 8
System.out.println(multiply.operate(5, 3)); // 15

Built-in Functional Interfaces (java.util.function)

java exampleWoHoTech

// Predicate<T> — condition check (returns boolean)
Predicate<Integer> isEven = n -> n % 2 == 0;
isEven.test(4); // true

// Function<T, R> — T input, R output
Function<String, Integer> length = s -> s.length();
length.apply("Hello"); // 5

// Consumer<T> — input, no output
Consumer<String> printer = s -> System.out.println(s);
printer.accept("Hello");

// Supplier<T> — no input, T output
Supplier<Double> random = () -> Math.random();
random.get(); // 0.XYZ

// BiFunction<T, U, R>
BiFunction<Integer, Integer, Integer> add = (a, b) -> a + b;
add.apply(3, 4); // 7

// UnaryOperator<T>
UnaryOperator<String> upper = s -> s.toUpperCase();
upper.apply("hello"); // "HELLO"

// BinaryOperator<T>
BinaryOperator<Integer> max = (a, b) -> a > b ? a : b;
max.apply(5, 3); // 5

Lambda Expression

Syntax

Functional Interface ke saath

Built-in Functional Interfaces (java.util.function)

Continue learning this concept

Lambda Expression

Syntax

Functional Interface ke saath

Built-in Functional Interfaces (java.util.function)

Continue learning this concept