Govt. Exams
Entrance Exams
Time complexity depends on the specific reduction operation, whether the lambda is stateless, and stream characteristics. Generally O(n), but parallelization overhead affects actual performance.
This is a curried function. curry.apply(5) returns a function that adds 5. Applying that with 3 gives 5 + 3 = 8.
Each flatMap creates intermediate streams. Deeply nested flatMap with lambdas can consume significant memory, especially with large datasets.
Collectors.toMap with key mapper (s -> s) produces String keys and value mapper (s -> s.length()) produces Integer values, resulting in Map<String, Integer>.
Sequential reduce is O(n). Parallel reduction can be O(log n) with a properly associative and commutative operation, enabling divide-and-conquer approach.
Lambda expressions don't propagate checked exceptions. They must be caught within the lambda body using try-catch.
Compiler uses target type (functional interface) to infer parameter types. If context is clear, explicit types not needed: list.forEach(x -> ...).
BiFunction concat = (a, b) -> a + b;
concat.apply("Java", "8", "Features");
BiFunction takes exactly 2 parameters. Passing 3 arguments is compilation error. apply() only accepts 2 arguments.
Function add = x -> y -> x + y;
System.out.println(add.apply(3).apply(5));
Curried function: add.apply(3) returns a Function that adds 3. .apply(5) on that adds 5 to 3, returning 8.
'? super T' allows writing T instances (contravariant), while '? extends T' allows safe reading (covariant). This combination enables flexible yet type-safe collection manipulation.
