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What is a thread pool?

Athreadpoolimprovesperformancebyreusingthreadstoexecutetasks.Insteadofcreatinganddestroyingthreadsforeachtask,apoolmaintainsidlethreadsthatpickuptasksfromaqueue,reducingoverheadandresourceconsumption.Keybenefitsincludeimprovedperformance,betterresour

Jun 30, 2025 am 01:08 AM

What are terminal stream operations?

Terminal operations are the last step in producing results or side effects in the JavaStream pipeline, which trigger the actual processing of the stream. Common terminal operations include: 1.forEach is used to perform operations on each element; 2.collect collects stream elements into a collection; 3. reduce merges elements into a single value; 4. findFirst/findAny returns the first or any element that matches; 5. allMatch/anyMatch/noneMatch checks whether the element meets the conditions; 6.count returns the number of elements in the stream; 7.toArray converts the stream into an array. Note when using: the stream can only be consumed once, some operations such as findFirst or

Jun 30, 2025 am 01:03 AM

java

What is the `transient` keyword?

ThetransientkeywordinJavameansavariableshouldnotbeserialized.1.Itexcludesfieldsfromserialization,suchassensitiveortemporarydata.2.Duringdeserialization,transientfieldsareresettodefaultvalues.3.Useitforfieldsthatshouldn'tpersist,likepasswordsorruntime

Jun 30, 2025 am 01:03 AM

What is a WAR file?

AWARfileisapackagedwebapplicationforJavaservers,containingcode,libraries,andconfigurationinastructuredformat.ItincludesWEB-INF/withweb.xml(servletdefinitions),classes/,lib/,andpublicresourceslikeHTMLandJSPoutsideWEB-INF.Tocreateone,followthestandardp

Jun 30, 2025 am 01:02 AM

What is the `this` keyword?

This points to the context of function execution in JavaScript, depending on how it is called. 1. When called as an object method, this points to the object; 2. When called independently, it points to the global object in non-strict mode, which is undefined in strict mode; 3. This inherits the outer context in the arrow function. Common problems include this pointing errors in event handling and callbacks, which can be solved by binding, saving references, or using arrow functions. call, apply, and bind can be used to explicitly specify this, where call and apply call immediately call the function, and bind generates the bound function. Mastering this behavior is crucial to writing effective code.

Jun 30, 2025 am 01:00 AM

How to create an array?

The key to creating an array is to select the appropriate method according to the programming language. The basic idea is to define a variable that can store multiple data items. 1. The way to declare arrays is slightly different in common languages: JavaScript uses letarr=[1,2,3], Python uses arr=[1,2,3], Java uses int[]arr={1,2,3}, C uses intarr[]={1,2,3}, and beginners are advised to start with Python or JavaScript. 2. The basic operations of an array include accessing elements (such as arr[0]), adding elements (such as arr.push or append), and deleting elements (such as arr.pop or splice). Note

Jun 30, 2025 am 12:59 AM

What is class loading in Java?

Java's class loading is a mechanism for JVM to load classes dynamically at runtime. Its core works by three class loaders at hierarchy and delegate model. 1. BootstrapClassLoader is responsible for loading the core class library; 2. ExtensionClassLoader is used to load the extension library; 3. ApplicationClassLoader loads classes in the application classpath. Class loading adopts on-demand loading strategies, which helps reduce memory overhead and improve startup efficiency. It is particularly critical in large applications (such as Spring, OSGi), web servers and plug-in systems, and can realize dynamic loading and isolation of classes. If the configuration is not correct, ClassNotFoundEx may be triggered

Jun 30, 2025 am 12:31 AM

java class loading

What are generics in Java?

GenericsinJavaenabletype-safereusablecodebyallowingclasses,interfaces,andmethodstooperateonanydatatype.IntroducedinJava5,theypreventruntimeerrorsbycatchingtypemismatchesatcompiletime,asseenwhenusingcollectionslikeListthatdisallowaddingincompatibletyp

Jun 30, 2025 am 12:28 AM

How to use the `static` keyword?

The static keyword is used in Java to modify variables, methods, and internal classes, and is at the class level rather than the instance level. 1. StaticVariables are shared by all objects, suitable for counter or constant definitions, and it is better to define constants using publicstaticfinal; 2. StaticMethods are called directly through the class name, and cannot access non-static members, and are suitable for tool classes and factory methods; 3. StaticBlocks are executed once during class loading and are used to initialize static resources or configurations; 4. StaticNestedClasses do not rely on external class instances to improve encapsulation and performance

Jun 30, 2025 am 12:19 AM

How to compare strings in Java?

You cannot use the == operator to compare string content in Java because it compares object references rather than content. The following methods should be used: 1. Use the .equals() method to determine whether the content is the same. This is the most commonly used and recommended method. Please note that strings that are not null are placed in front of them to avoid null pointer exceptions; 2. Use the .equalsIgnoreCase() method to ignore case comparisons, which is suitable for handling user input or configuration files. 3. Use the .compareTo() method to compare string order and size, return 0 to mean equality, and negative numbers indicate the current string before the parameter string, and positive numbers are the opposite, and are suitable for sorting or alphabetical processing; 4. Avoid using == to compare

Jun 30, 2025 am 12:12 AM

How to create a thread?

To create an engagement discussion post, you must first clarify the topic, such as "Why is remote working more and more difficult to manage now?" or "I spent 3 months optimizing my early-wake habits. These 5 methods are the most effective", so that people can see the core of the content at a glance. Secondly, use numbers or steps to enhance readability, such as three steps: the first step is to identify the problem, the second step is to analyze the cause, and the third step is to provide a solution. At the same time, sentence patterns such as "I discovered a rule" and "I tried 3 methods, only this is useful" can be used to enhance the attractiveness. Furthermore, control the rhythm, tell a small dot in each tweet, keep it simple, 1 to 2 sentences, and appropriately split the complex content, interspersed with questions or summary sentences to stimulate interest. The last few should be carefully designed to avoid hasty endings, and can be used to introduce them by invitation interaction or summary.

Jun 29, 2025 am 01:32 AM

What is the `super` keyword?

The super keyword is used to call the parent class's methods or access the parent class attributes. Common uses include calling the parent class methods, initializing the parent class constructor, and handling method override and multiple inheritance. 1. When calling the parent class method, you can use super.method() in the subclass to preserve the original behavior; 2. When initializing the constructor, you need to use super() to ensure that the parent class is initialized correctly; 3. In multiple inheritance, super() calls the next parent class method in the order of method parsing, making the inheritance chain clearer and easier to maintain. Use super rationally to improve code maintainability, but excessive use can cause logical confusion.

Jun 29, 2025 am 01:31 AM

oop super keywords

What is a HashSet?

HashSet is a collection based on a hash table, with elements that are non-repeatable and highly query efficient. Its core features include: 1. Unordered, elements have no fixed order and cannot be accessed through the index; 2. Uniqueness, adding duplicate values ??will be automatically ignored; 3. Efficient query, the time complexity of insertion, deletion and search is close to O(1). Compared with List, List is ordered, allows repetition and has lower query efficiency. Common operations include add(), remove() removal, contains() judgment existence, and size() obtaining quantity. When using it, you need to pay attention to overriding the equals() and hashCode() methods for custom classes. Suitable for deduplication, quick search and collection operation scenarios.

Jun 29, 2025 am 01:30 AM

data structure hashset

What is the Java Collections Framework?

The Java Collection Framework (JCF) is a set of classes and interfaces for storing and manipulating data collections, providing a unified and efficient way to process core data. It mainly includes three core interfaces: 1.Collection interface, which derives List, Set and Queue. List is an ordered and repeatable collection. Common implementations include ArrayList and LinkedList; 2.Set is a collection of non-repeated elements, such as HashSet and TreeSet; 3.Map is used to store key-value pairs, and common implementations include HashMap and TreeMap. Implementation classes are selected according to different scenarios, such as frequent access to ArrayList, insert and delete multiple uses LinkedList, go to

Jun 29, 2025 am 01:29 AM

java collection