Java 8 Features

 Java 8  feature list

1. Lambda Expressions

java

List<String> names = Arrays.asList("Ravi", "Anil", "Viswa");
names.forEach(n -> System.out.println(n));

👉 Useful for concise functional programming.

2. Method References

java

names.forEach(System.out::println);

👉 Cleaner syntax when reusing existing methods.

3. Default & Static Methods in Interfaces

java

interface Vehicle {
    default void start() { System.out.println("Starting..."); }
    static void info() { System.out.println("Vehicle info"); }
}

👉 Allows evolving APIs without breaking old code.

4. Stream API

java

List<Integer> nums = Arrays.asList(1,2,3,4,5);
int sum = nums.stream().filter(n -> n%2==0).mapToInt(n->n).sum();
System.out.println(sum); // 6

👉 Declarative data processing.

5. Optional Class

java

Optional<String> name = Optional.ofNullable(null);
System.out.println(name.orElse("Default")); // Default

👉 Avoids NullPointerException.

6. New Date/Time API

java

LocalDate today = LocalDate.now();
LocalDate nextWeek = today.plusWeeks(1);
System.out.println(nextWeek);

👉 Immutable, thread-safe time handling.

7. CompletableFuture

java

CompletableFuture.supplyAsync(() -> "Hello")
                 .thenAccept(System.out::println);

👉 Asynchronous programming made easy.

8. Nashorn JavaScript Engine

java

ScriptEngine engine = new ScriptEngineManager().getEngineByName("nashorn");
engine.eval("print('Hello from JS')");

👉 Embeds JavaScript in JVM.

9. Base64 Encoding/Decoding

java

String encoded = Base64.getEncoder().encodeToString("data".getBytes());
System.out.println(encoded);

👉 Secure data transmission.

10. Parallel Array Sorting

java

int[] arr = {5,3,8,1};
Arrays.parallelSort(arr);
System.out.println(Arrays.toString(arr)); // [1,3,5,8]

👉 Faster sorting on large arrays.

11. Repeating Annotations

java

@Schedule(day="Monday")
@Schedule(day="Friday")
class Meeting {}

👉 Apply same annotation multiple times.

12. Type Annotations

java

List<@NonNull String> list = new ArrayList<>();

👉 More precise type checking.

13. Parameter Name Reflection

java

Method m = MyClass.class.getMethod("myMethod", String.class);
for (Parameter p : m.getParameters()) {
    System.out.println(p.getName());
}

👉 Useful for frameworks and debugging.

Java Stream API : Java 8 Feature

📌 Stream API Quick Reference Sheet

Method	Type	Functional Interface	Purpose	Example
forEach()	Terminal	Consumer<T>	Perform an action on each element	list.stream().forEach(System.out::println);
filter()	Intermediate	Predicate<T>	Keep only elements that match a condition	list.stream().filter(n -> n > 10);
map()	Intermediate	Function<T,R>	Transform each element	list.stream().map(String::length);
flatMap()	Intermediate	Function<T,Stream<R>>	Flatten nested structures	list.stream().flatMap(List::stream);
sorted()	Intermediate	Comparator<T>	Sort elements	list.stream().sorted();
distinct()	Intermediate	—	Remove duplicates	list.stream().distinct();
limit()	Intermediate	—	Restrict to first n elements	list.stream().limit(5);
skip()	Intermediate	—	Skip first n elements	list.stream().skip(3);
peek()	Intermediate	Consumer<T>	Debug/log elements	list.stream().peek(System.out::println);
reduce()	Terminal	BinaryOperator<T>	Combine into single result	list.stream().reduce(0, Integer::sum);
collect()	Terminal	Collector<T,A,R>	Gather results into a collection	list.stream().collect(Collectors.toList());
anyMatch() / allMatch() / noneMatch()	Terminal	Predicate<T>	Check conditions across elements	list.stream().anyMatch(n -> n > 0);
findFirst() / findAny()	Terminal	—	Retrieve one element	list.stream().findFirst();

forEach in Stream : The forEach() method in Java’s Stream API is used to iterate over each element of the stream and perform an action on it. It’s a terminal operation, meaning once you call forEach(), the stream pipeline is consumed and cannot be reused.

List<String> names = Arrays.asList("Alice", "Bob", "Charlie");

names.stream()

     .forEach(System.out::println); // Consumer

filter Method : The filter() method in Java’s Stream API is used to select elements that match a given condition. It’s an intermediate operation, meaning it transforms the stream but doesn’t consume it

List<Integer> numbers = Arrays.asList(1, 2, 3, 4, 5, 6);

List<Integer> evens = numbers.stream()

                             .filter(n -> n % 2 == 0) // Predicate

                             .collect(Collectors.toList());

System.out.println(evens);

Filter method on Strings as below

List<String> names = Arrays.asList("Ravi", "Anil", "Viswa", "Rajesh", "Sita");

List<String> longNames = names.stream()

                              .filter(name -> name.length() > 4)

                              .collect(Collectors.toList());

System.out.println(longNames);

findFirst,findAny,Max,min & reduce will have optiona as return type to avoid null pointer exception