URL is the abbreviation of Uniform Resource Locator (Uniform Resource Locator), which represents the address of a resource on the Internet. Through URLs, users can access various network resources, such as common WWW and FTP sites. A browser can parse a given URL to find the corresponding file or other resource on the network.
URL class
The java.net package contains a class URL specially used to process URLs, and you can get the URL related Information, such as the protocol name and host name of the URL.
URLConnection class
After completing the definition of URL, you can then obtain the communication connection of the URL. In the java.net package, a special URLConnection class is defined to represent the communication connection established with the URL. The object of the URLConnection class is obtained using the openConnection() method of the URL class.
Example:
Use the URL and URLConnection classes to obtain the link to the Baidu homepage and output its page information to the console. The main steps are as follows.
(1) Create a class, write the main() method, create a URL object in this method, and then pass in the parameter "http://www.baidu.com/" and output the URL The relevant information, the code is as follows.
package ch16; import java.io.IOException; import java.io.InputStream; import java.net.URL; import java.net.URLConnection; public class URLDemo { public static void main(String[] args) { try { URL url=new URL("http://www.baidu.com/"); System.out.println("协议:" + url.getProtocol());//获取该 URL 的协议名。 System.out.println("主机:" + url.getHost());//获取该 URL 的主机名。 System.out.println("端口:" + url.getPort());//获取该 URL 的端口号,如果没有设置端口,返回 -1。 InputStream in; } catch(IOException e) { //TODO 自动生成的 catch 块 e.printStackTrace(); } } }
(2) Continue to add code in the try module of the main() method, obtain the URLConnection object, read the page source code through the input stream and output the information to the console, code As follows.
URLConnection uc=url.openConnection(); in=uc.getInputStream();//返回从此打开的链接读取的输入流。 byte[] b=new byte[1024]; int len; while((len=in.read(b))!=-1) { System.out.println(new String(b,0,len)); } in.close();
(3) Run the program and the execution results are as follows.
协议:http 主机:www.baidu.com 端口:-1 nbsp;html> <!--STATUS OK--> <meta> <meta><meta> <link>
Related learning recommendations: java basic tutorial
The above is the detailed content of What is url in java. For more information, please follow other related articles on the PHP Chinese website!

Javaispopularforcross-platformdesktopapplicationsduetoits"WriteOnce,RunAnywhere"philosophy.1)ItusesbytecodethatrunsonanyJVM-equippedplatform.2)LibrarieslikeSwingandJavaFXhelpcreatenative-lookingUIs.3)Itsextensivestandardlibrarysupportscompr

Reasons for writing platform-specific code in Java include access to specific operating system features, interacting with specific hardware, and optimizing performance. 1) Use JNA or JNI to access the Windows registry; 2) Interact with Linux-specific hardware drivers through JNI; 3) Use Metal to optimize gaming performance on macOS through JNI. Nevertheless, writing platform-specific code can affect the portability of the code, increase complexity, and potentially pose performance overhead and security risks.

Java will further enhance platform independence through cloud-native applications, multi-platform deployment and cross-language interoperability. 1) Cloud native applications will use GraalVM and Quarkus to increase startup speed. 2) Java will be extended to embedded devices, mobile devices and quantum computers. 3) Through GraalVM, Java will seamlessly integrate with languages such as Python and JavaScript to enhance cross-language interoperability.

Java's strong typed system ensures platform independence through type safety, unified type conversion and polymorphism. 1) Type safety performs type checking at compile time to avoid runtime errors; 2) Unified type conversion rules are consistent across all platforms; 3) Polymorphism and interface mechanisms make the code behave consistently on different platforms.

JNI will destroy Java's platform independence. 1) JNI requires local libraries for a specific platform, 2) local code needs to be compiled and linked on the target platform, 3) Different versions of the operating system or JVM may require different local library versions, 4) local code may introduce security vulnerabilities or cause program crashes.

Emerging technologies pose both threats and enhancements to Java's platform independence. 1) Cloud computing and containerization technologies such as Docker enhance Java's platform independence, but need to be optimized to adapt to different cloud environments. 2) WebAssembly compiles Java code through GraalVM, extending its platform independence, but it needs to compete with other languages for performance.

Different JVM implementations can provide platform independence, but their performance is slightly different. 1. OracleHotSpot and OpenJDKJVM perform similarly in platform independence, but OpenJDK may require additional configuration. 2. IBMJ9JVM performs optimization on specific operating systems. 3. GraalVM supports multiple languages and requires additional configuration. 4. AzulZingJVM requires specific platform adjustments.

Platform independence reduces development costs and shortens development time by running the same set of code on multiple operating systems. Specifically, it is manifested as: 1. Reduce development time, only one set of code is required; 2. Reduce maintenance costs and unify the testing process; 3. Quick iteration and team collaboration to simplify the deployment process.


Hot AI Tools

Undresser.AI Undress
AI-powered app for creating realistic nude photos

AI Clothes Remover
Online AI tool for removing clothes from photos.

Undress AI Tool
Undress images for free

Clothoff.io
AI clothes remover

Video Face Swap
Swap faces in any video effortlessly with our completely free AI face swap tool!

Hot Article

Hot Tools

mPDF
mPDF is a PHP library that can generate PDF files from UTF-8 encoded HTML. The original author, Ian Back, wrote mPDF to output PDF files "on the fly" from his website and handle different languages. It is slower than original scripts like HTML2FPDF and produces larger files when using Unicode fonts, but supports CSS styles etc. and has a lot of enhancements. Supports almost all languages, including RTL (Arabic and Hebrew) and CJK (Chinese, Japanese and Korean). Supports nested block-level elements (such as P, DIV),

VSCode Windows 64-bit Download
A free and powerful IDE editor launched by Microsoft

SublimeText3 Chinese version
Chinese version, very easy to use

Zend Studio 13.0.1
Powerful PHP integrated development environment

ZendStudio 13.5.1 Mac
Powerful PHP integrated development environment
