Basic knowledge of Java backend (2)

1. What are generics in Java? How to use generics?

Generics in Java are a parameterized type that can be parameterized to achieve code reuse. You can use generics in classes, interfaces, and methods, and pass type parameters to generics to support multiple types. Generics can be implemented using generic classes, generic interfaces, and generic methods. Generics can also be used to achieve type safety, code readability, and more.

2. What is serialization in Java? How to achieve serialization of Java objects?

Serialization in Java refers to the process of converting a Java object into a stream of bytes for transmission over a network or storage into a file. The serialization of Java objects can be achieved by implementing the Serializable interface, which has no methods and is only used to mark that the class can be serialized. Serialization can use the ObjectOutputStream class to write objects to the output stream, and deserialization can use the ObjectInputStream class to read objects from the input stream.

3. What are Lambda Expressions in Java? How to use Lambda expressions?

Java Lambda expression is a new syntax structure introduced in Java 8, which provides a concise way to declare an anonymous function and pass it as a method parameter or return value. Lambda expressions allow us to write code in a more concise manner, making the code easier to understand and maintain.

Lambda expressions consist of three parts: parameter list, arrow notation, and function body. The body of a function can be an expression or a block of code, and Lambda expressions can be used with functional interfaces, which are interfaces that contain only one abstract method. With Lambda expressions, functional interfaces can be instantiated with less code.

Here is an example of a simple Lambda expression:

(x, y) -> x + y

This Lambda expression takes two integer parameters x and y and returns their sum. The arrow symbol represents the separator from the parameter list to the function body, where the function body is a simple expression x + y. The grammatical structure of Lambda expressions is relatively simple, but its powerful functions and wide application make it an important feature in Java 8.

4. What is thread safety in Java?

Thread safety refers to ensuring the correctness and consistency of resources when multiple threads access the same resource at the same time in a multi-threaded environment. Thread safety in Java can be achieved by using synchronized keyword or Lock object.

5. What are generics in Java?

Generics are a feature in Java that can make code more general and safe. Using generics allows type safety to be checked at compile time, thus avoiding type errors at runtime. Generics in Java are mainly implemented through generic classes, generic interfaces, and generic methods.

6. What are the commonly used frameworks and libraries in Java?

There are many commonly used frameworks and libraries in Java, including Spring, Hibernate, MyBatis, Netty, Hadoop, etc. Spring is an open source application framework for building enterprise-level Java applications, mainly providing functions such as dependency injection, AOP, and transaction management. Hibernate and MyBatis are two popular ORM frameworks used to simplify the interaction of Java applications with relational databases. Netty is a high-performance network programming framework for building scalable network applications. Hadoop is a distributed computing platform for processing massive data and large-scale computing tasks.

7. What is a distributed system in Java?

A distributed system is a system architecture that distributes different components of the system on multiple physical nodes, communicates and coordinates through network protocols, thereby improving the scalability, reliability and availability of the system. Distributed systems in Java can be implemented by using technologies such as RPC frameworks, message queues, and distributed caches.

8. What is AOP in Java?

AOP (Aspect-Oriented Programming) is a programming idea that is used to decouple different concerns in the system and improve the maintainability and scalability of the code. AOP is mainly realized through concepts such as aspects, connection points, and notifications. It can cut some behaviors of the system horizontally, and can dynamically weave aspect logic at runtime.

9. What is the singleton pattern in Java? Please list several implementations of the singleton pattern.

The singleton pattern is a design pattern used to ensure that there is only one instance of a class and to provide a global point of access. The singleton mode in Java can be implemented in several ways such as lazy man style, hungry man style, double check lock and so on. Among them, the lazy-style singleton mode needs to use synchronization locks to achieve thread safety in a multi-threaded environment, while the hungry-style singleton mode can ensure thread safety through the class loading mechanism.

10. What is the garbage collection mechanism in Java?

Garbage collection (GC) is a mechanism in the JVM to automatically release unused memory space to avoid memory leaks and memory overflow problems. The JVM implements garbage collection through the garbage collector, which is mainly divided into several different garbage collection algorithms such as Serial GC, Parallel GC, CMS GC, and G1 GC.