To make the program run, the JSON-lib package must be introduced. The JSON-lib package also depends on the following JAR packages:
1.commons-lang.jar
2.commons-beanutils.jar
3.commons-collections.jar
4.commons-logging.jar
5.ezmorph.jar
6.json-lib-2.2.2-jdk15.jar
2. JSONObject object usage
The JSON-lib package is a set of beans, collections, maps, java arrays and A package for converting XML and JSON to and from each other. In this example, we will create JSONObject objects using the JSONObject class and then we print the values of these objects. In order to use JSONObject objects, we need to introduce the "net.sf.json" package. To add elements to an object, we use the put() method.
import net.sf.json.JSONArray; import net.sf.json.JSONObject; public class JSONObjectSample { //创建JSONObject对象 private static JSONObject createJSONObject(){ JSONObject jsonObject = new JSONObject(); jsonObject.put("name", "kevin"); jsonObject.put("Max.score", new Integer(100)); jsonObject.put("Min.score", new Integer(50)); jsonObject.put("nickname", "picglet"); return jsonObject; } public static void main(String[] args) { JSONObject jsonObject = JSONObjectSample.createJSONObject(); //输出jsonobject对象 System.out.println("jsonObject==>"+jsonObject); //判读输出对象的类型 boolean isArray = jsonObject.isArray(); boolean isEmpty = jsonObject.isEmpty(); boolean isNullObject = jsonObject.isNullObject(); System.out.println("isArray:"+isArray+" isEmpty:"+isEmpty+" isNullObject:"+isNullObject); //添加属性 jsonObject.element("address", "swap lake"); System.out.println("添加属性后的对象==>"+jsonObject); //返回一个JSONArray对象 JSONArray jsonArray = new JSONArray(); jsonArray.add(0, "this is a jsonArray value"); jsonArray.add(1,"another jsonArray value"); jsonObject.element("jsonArray", jsonArray); JSONArray array = jsonObject.getJSONArray("jsonArray"); System.out.println("返回一个JSONArray对象:"+array); //添加JSONArray后的值 //{"name":"kevin","Max.score":100,"Min.score":50,"nickname":"picglet","address":"swap lake", //"jsonArray":["this is a jsonArray value","another jsonArray value"]} System.out.println(jsonObject); //根据key返回一个字符串 String jsonString = jsonObject.getString("name"); System.out.println("jsonString==>"+jsonString); } } import net.sf.json.JSONArray; import net.sf.json.JSONObject; public class JSONObjectSample { //创建JSONObject对象 private static JSONObject createJSONObject(){ JSONObject jsonObject = new JSONObject(); jsonObject.put("name", "kevin"); jsonObject.put("Max.score", new Integer(100)); jsonObject.put("Min.score", new Integer(50)); jsonObject.put("nickname", "picglet"); return jsonObject; } public static void main(String[] args) { JSONObject jsonObject = JSONObjectSample.createJSONObject(); //输出jsonobject对象 System.out.println("jsonObject==>"+jsonObject); //判读输出对象的类型 boolean isArray = jsonObject.isArray(); boolean isEmpty = jsonObject.isEmpty(); boolean isNullObject = jsonObject.isNullObject(); System.out.println("isArray:"+isArray+" isEmpty:"+isEmpty+" isNullObject:"+isNullObject); //添加属性 jsonObject.element("address", "swap lake"); System.out.println("添加属性后的对象==>"+jsonObject); //返回一个JSONArray对象 JSONArray jsonArray = new JSONArray(); jsonArray.add(0, "this is a jsonArray value"); jsonArray.add(1,"another jsonArray value"); jsonObject.element("jsonArray", jsonArray); JSONArray array = jsonObject.getJSONArray("jsonArray"); System.out.println("返回一个JSONArray对象:"+array); //添加JSONArray后的值 //{"name":"kevin","Max.score":100,"Min.score":50,"nickname":"picglet","address":"swap lake", //"jsonArray":["this is a jsonArray value","another jsonArray value"]} System.out.println(jsonObject); //根据key返回一个字符串 String jsonString = jsonObject.getString("name"); System.out.println("jsonString==>"+jsonString); } }

JavaScript's application in the real world includes front-end and back-end development. 1) Display front-end applications by building a TODO list application, involving DOM operations and event processing. 2) Build RESTfulAPI through Node.js and Express to demonstrate back-end applications.

The main uses of JavaScript in web development include client interaction, form verification and asynchronous communication. 1) Dynamic content update and user interaction through DOM operations; 2) Client verification is carried out before the user submits data to improve the user experience; 3) Refreshless communication with the server is achieved through AJAX technology.

Understanding how JavaScript engine works internally is important to developers because it helps write more efficient code and understand performance bottlenecks and optimization strategies. 1) The engine's workflow includes three stages: parsing, compiling and execution; 2) During the execution process, the engine will perform dynamic optimization, such as inline cache and hidden classes; 3) Best practices include avoiding global variables, optimizing loops, using const and lets, and avoiding excessive use of closures.

Python is more suitable for beginners, with a smooth learning curve and concise syntax; JavaScript is suitable for front-end development, with a steep learning curve and flexible syntax. 1. Python syntax is intuitive and suitable for data science and back-end development. 2. JavaScript is flexible and widely used in front-end and server-side programming.

Python and JavaScript have their own advantages and disadvantages in terms of community, libraries and resources. 1) The Python community is friendly and suitable for beginners, but the front-end development resources are not as rich as JavaScript. 2) Python is powerful in data science and machine learning libraries, while JavaScript is better in front-end development libraries and frameworks. 3) Both have rich learning resources, but Python is suitable for starting with official documents, while JavaScript is better with MDNWebDocs. The choice should be based on project needs and personal interests.

The shift from C/C to JavaScript requires adapting to dynamic typing, garbage collection and asynchronous programming. 1) C/C is a statically typed language that requires manual memory management, while JavaScript is dynamically typed and garbage collection is automatically processed. 2) C/C needs to be compiled into machine code, while JavaScript is an interpreted language. 3) JavaScript introduces concepts such as closures, prototype chains and Promise, which enhances flexibility and asynchronous programming capabilities.

Different JavaScript engines have different effects when parsing and executing JavaScript code, because the implementation principles and optimization strategies of each engine differ. 1. Lexical analysis: convert source code into lexical unit. 2. Grammar analysis: Generate an abstract syntax tree. 3. Optimization and compilation: Generate machine code through the JIT compiler. 4. Execute: Run the machine code. V8 engine optimizes through instant compilation and hidden class, SpiderMonkey uses a type inference system, resulting in different performance performance on the same code.

JavaScript's applications in the real world include server-side programming, mobile application development and Internet of Things control: 1. Server-side programming is realized through Node.js, suitable for high concurrent request processing. 2. Mobile application development is carried out through ReactNative and supports cross-platform deployment. 3. Used for IoT device control through Johnny-Five library, suitable for hardware interaction.


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