Java 8 introduced significant enhancements to the Java programming language, including the introduction of several new features and improvements to the API. Here are some key aspects of the Java 8 API:

1. Lambda Expressions: One of the most notable features of Java 8 is lambda expressions. Lambda expressions allow you to express instances of single-method interfaces (functional interfaces) using a concise syntax. This feature greatly simplifies coding and enables the use of functional programming paradigms in Java.

2. Stream API: Java 8 introduced the Stream API, which provides a powerful way to work with collections and sequences of data. It allows you to perform operations like filtering, mapping, and reducing on collections in a more functional and declarative style.

3. Default Methods: Default methods enable you to add new methods to interfaces without breaking existing implementations. This feature is useful for evolving interfaces over time.

4. Method References: Method references allow you to refer to methods or constructors using a shorter syntax. They are often used in conjunction with lambda expressions to improve code readability.

5. Functional Interfaces: Java 8 introduced a new annotation called @FunctionalInterface to indicate that an interface is intended to be used as a functional interface. Functional interfaces are interfaces with a single abstract method and can be used effectively with lambda expressions.

6. Date and Time API: Java 8 introduced a new Date and Time API (java.time) that addresses the shortcomings of the old java.util.Date and java.util.Calendar classes. It provides a more comprehensive and accurate representation of dates and times.

7. Optional: The Optional class was introduced to represent an optional value that may or may not be present. It helps prevent null pointer exceptions and encourages more robust code.

8. New Collections Features: Java 8 added several new methods to the Collection interface, including forEach, removeIf, and stream-related methods, making it easier to work with collections.

9. Nashorn JavaScript Engine: Java 8 included the Nashorn JavaScript engine, which allows you to execute JavaScript code from within Java applications.

10. Concurrency Enhancements: Java 8 introduced the CompletableFuture class for asynchronous and non-blocking programming. It also improved the ConcurrentHashMap class with new methods for concurrent data manipulation.