Frequent Java questions and answers for interviews

High-frequency Java questions and answers for interviews

With the widespread application of the Java language, it is very common for Java programmers to encounter various Java problems during interviews. Therefore, it is very important to understand common Java questions and answers. This article summarizes some frequently asked Java interview questions and the best answers. I hope this knowledge can help you stand out in the interview.

1. What is the difference between Java and JavaScript?

This is a common question. It should be noted that Java and JavaScript are two completely different languages. Java is an object-oriented programming language primarily used for building enterprise-level applications. JavaScript is a web-based scripting language that can be used on the client or server side.

The best answer is: Java and JavaScript are two different programming languages. Java is mainly used for building enterprise-level applications, while JavaScript is mainly used for web front-end development.

2. How to create a singleton pattern?

The singleton pattern is a very common pattern that ensures that only one object instance exists. There are many ways to create a singleton pattern, including hungry singletons, lazy singletons, thread-safe singletons, etc.

The best answer is: Common methods of creating singleton patterns include hungry singletons, lazy singletons, and thread-safe singletons. Each method has its advantages and disadvantages, and you need to choose the appropriate method according to the situation.

3. What are the functions of hashCode() and equals() methods?

hashCode() and equals() are two important methods that are used to compare objects for equality in Java.

ThehashCode() method returns the hash code of the object, which is usually used to find the object in the hash table. The equals() method is used to compare whether objects are equal. If the objects are equal, it returns true, otherwise it returns false.

The best answer is: hashCode() and equals() methods are two methods in the Java Object class, used to compare objects for equality. The hashCode() method returns the hash code of the object, and the equals() method is used to compare whether the objects are equal.

4. What is the difference between List and Set?

List and Set are two commonly used container types in Java collections, and they have many differences.

List is an ordered container that can contain repeated elements. Lists are usually used to store data that need to be sorted in a specific order.

Set is an unordered container and cannot contain duplicate elements. Sets are usually used to store data that need to be sorted according to uniqueness.

The best answer is: List is an ordered container that can contain repeated elements. Lists are usually used to store data that need to be sorted in a specific order. Set is an unordered container and cannot contain duplicate elements. Sets are usually used to store data that need to be sorted according to uniqueness.

5. What are the exceptions in the program? How are they processed?

Exception is a special event that has the ability to disrupt the normal execution of a program. In Java, when an exception occurs in a program, an exception object is usually thrown. This exception object encapsulates the type and cause of the exception. Programs can use try-catch statements to catch and handle exceptions.

The best answer is: An exception is a special event that disrupts the normal execution flow of the program. When an exception occurs in a program, an exception object is usually thrown. Programs can use try-catch statements to catch and handle exceptions. Or throw the exception up and handle it where it's called.

6. What is polymorphism? How to implement polymorphism in Java?

Polymorphism means that the same object will show different behaviors in different situations. In Java, polymorphism is achieved through method overloading and method overriding.

Method overloading refers to defining two or more methods with the same name in the same class, but with different parameter lists. Method overloading makes calling methods more convenient.

Method overriding refers to overriding the methods of the parent class in the subclass. Subclasses can add new features to methods or modify the behavior of parent class methods.

The best answer is: Polymorphism means that the same object will show different behaviors in different situations. In Java, polymorphism is achieved through method overloading and method overriding. Method overloading refers to defining two or more methods with the same name in the same class, but different parameter lists. Method overriding refers to rewriting the methods of the parent class in the subclass, making it more convenient to call the method.

Summary

Java is a very powerful programming language. Mastering Java skills can make you more competitive in the workplace. This article gives some common Java questions and answers, hoping to help you succeed in the interview. Of course, these questions are only a small part of the Java knowledge system. If you want to achieve higher achievements in the field of Java, it is recommended to continue to learn and practice Java programming skills.

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