Learn from the Expression Language 3.0 API in the Java Class Library

Java expression language (EL) is part of the Java class library, which is used to dynamically calculate and access expressions in Java applications.EL 3.0 API is the latest version introduced by the Java EE 7 platform, which provides some new functions and improvements, enabling developers to use EL to process and operate expressions in applications more conveniently. EL allows developers to reference and operate variables, methods and attributes in the application through simple syntax.It provides a unified standard method for dynamic computing and processing expressions, and can be seamlessly integrated with various Java technologies such as Javaseer Pages (JSP) and JavaServer Faces (JSF).The main characteristics of EL include: 1. Simple grammar: EL provides a simple and intuitive expression syntax, enabling developers to easily quote and operate the value of the expression expression. 2. Powerful functions: EL supports various common expression operations, including arithmetic operations, logical operations, string stitching, collection operations, etc. 3. Object navigation: EL allows the attributes and methods of the object to access the object's attributes and methods to enable developers to easily navigate and operate complex object structures. 4. Integration: EL can be seamlessly integrated into various Java technology, and closely cooperates with other parts of these technologies (such as the JSP label library, JSF form binding, etc.) to provide more powerful functions and more flexible expressionsdeal with. Below is an example of Java code using EL 3.0 API, showing how to use EL to calculate and display expressions in a simple web application: import javax.el.*; public class Main { public static void main(String[] args) { // Create EL expression engine ELProcessor elp = new ELProcessor(); // Define variables elp.defineBean("x", 10); elp.defineBean("y", 5); // Calculate expression Object result = elp.eval("x + y"); // Print results System.out.println ("Calculation Result:" + Result); } } The above code creates an ElProcessor object, and uses the `Definebean` method to define two variable x and y, and then use the` Eval` method to calculate the value of the expression "x + y" and output the result.Through EL 3.0 API, we can easily calculate and process expressions to achieve dynamic computing and display functions. In short, EL 3.0 API is an important part of the Java class library. It provides developers with a convenient way to process and operate expression values by providing simple and powerful grammar and functions.Whether in web applications or in other Java applications, EL is a very useful tool to help developers write code more efficiently and achieve various dynamic functions.