Java 8 features

Java 8 introduced several significant features that enhanced the language's functionality and ease of use. Here are some of the key features:

1. **Lambda Expressions**:

- Enable functional programming by allowing you to treat functionality as a method argument or code as data.

- Syntax: `(parameters) -> expression` or `(parameters) -> { statements; }`

2. **Functional Interfaces**:

- An interface with exactly one abstract method.

- Can be annotated with `@FunctionalInterface`.

- Examples: `Runnable`, `Comparator`, `Callable`.

3. **Stream API**:

- Provides a new abstraction for processing sequences of elements (like collections) in a functional style.

- Supports operations like filter, map, reduce, collect, etc.

- Example: `list.stream().filter(x -> x > 10).collect(Collectors.toList());`

4. **Default Methods in Interfaces**:

- Allow interfaces to have methods with implementation without affecting the classes that implement the interface.

- Syntax: `default void methodName() { /* implementation */ }`

5. **Method References**:

- Shorthand notation for lambda expressions to call methods.

- Types: Reference to a static method, instance method, constructor.

- Example: `System.out::println`

6. **Optional Class**:

- A container object which may or may not contain a non-null value.

- Helps to avoid `NullPointerException`.

- Example: `Optional<String> optional = Optional.of("value");`

7. **New Date and Time API (java.time package)**:

- Introduced new classes like `LocalDate`, `LocalTime`, `LocalDateTime`, `ZonedDateTime`, etc.

- Immutable and thread-safe.

- Example: `LocalDate today = LocalDate.now();`

8. **Nashorn JavaScript Engine**:

- A new JavaScript engine to replace the old Rhino engine.

- Allows embedding JavaScript code within Java applications.

9. **Parallel Array Sorting**:

- New utility methods in `Arrays` class for parallel sorting.

- Example: `Arrays.parallelSort(array);`

10. **Type Annotations and Repeating Annotations**:

- Annotations can be applied to any type use, not just declarations.

- Repeating annotations allow the same annotation to be applied multiple times to a single element.

11. **CompletableFuture**:

- A new class for asynchronous programming.

- Allows chaining of tasks and handling of exceptions.

12. **StringJoiner**:

- A utility to construct sequences of characters separated by a delimiter.

- Example: `StringJoiner joiner = new StringJoiner(", "); joiner.add("one").add("two");`

These features have made Java more powerful and flexible, especially for functional programming and handling concurrency. If you need more detailed examples or explanations on any of these features, feel free to ask!