Learn about the basic principles of the 'Contracts for Java' framework in the Java class library

Title: The basic principles of the 'Contracts for Java' framework in the Java class library Summary: Contracts for Java (CFJ) is an annotated Java class library that is used in the programming and verification of the front conditions, rear conditions, and unchanged agreement to define and verify the code.This article will introduce the basic principles of the CFJ framework and provide some Java code examples to illustrate its use. 1 Overview Contracts for Java is a lightweight framework, which aims to enhance the readability, maintenance and reliability of the Java code by adding a agreement.Based on method -level annotations, it describes and verified the behavior of formalization on code. 2. Principles The CFJ framework specifies the agreement by adding annotations to the method statement.Common annotations include: -@Requires: The front conditions for specifying the method, the conditions that must be met before the description method calls. -@ENSURES: The rear conditions for specified methods, the conditions that must be met after the description method calls. -@Invariant: For the unable variable formula for specified classes, describing the status of the class, the conditions that must be met at any time. These annotations can be applied to the parameters, return values and class fields of the method.When running, the CFJ framework will use the conditions defined in the annotation to verify the code.If the verification fails, the corresponding abnormalities are thrown to instructions to violate some agreement. 3. Example The following example demonstrates how to use the Contracts for Java framework to define and verify the agreement: public class MathUtils { @Requires("a > 0 && b > 0") @Ensures("result > 0") public static int multiply(int a, int b) { return a * b; } } public class Main { public static void main(String[] args) { int result = MathUtils.multiply(5, 6); System.out.println("Result: " + result); } } In the above example, the Multiply method uses @Requires annotations to specify the front conditions (A and B must be greater than 0), and the rear conditions are specified using @ENSURES annotations (the result must be greater than 0).When running, if the Multiply method is called, it will not meet the front conditions or the results that are not met with rear conditions, and it will throw an exception. Using the Contracts for Java framework, we can clearly describe and verify the agreement of the code to improve the reliability and maintenance of the code.By adding these agreements to the code, we can better understand the behavior of the code and conduct static and dynamic verification of the correctness of the code. Summarize Contracts for Java framework provides a simple and powerful way to define and verify the Java code.It can enhance the readability of code, provide static and dynamic agreed verification, and help developers better understand and maintain code.Using this framework, we can design and implement Java applications in a more systematic and reliable way.