Detailed application cases of the 'Contracts for Java' framework in the Java class library

Application case of the 'Contracts for Java' framework in the Java class library 'Contracts for Java' is a framework in the Java class library to help developers write more robust, maintenance and easy -to -understand code.It provides a way to define and enforce the front conditions, rear conditions, and classes of the code, and verify these conditions by asserting and exceptions. By using 'Contracts for Java', developers can express their intentions in a statement in a statement and ensure that the code follows these constraints during runtime.This helps improve the readability, maintenance and reliability of the code. The following is a simple application case, showing how to use the 'Contracts for Java' framework. Case: Bank account Suppose we want to implement a bank account class, which has the function of deposit and withdrawal.In this case, we will use "Contracts for Java" to define some constraints and ensure that the code meets these constraints. First, we need to add the dependencies of the 'Contracts for Java' framework to the project. Maven dependence: <dependency> <groupId>org.jetbrains.contract</groupId> <artifactId>contract</artifactId> <version>1.2.4</version> </dependency> Gradle dependencies: implementation 'org.jetbrains.contract:contract:1.2.4' Now, we can define the bank account class and use the 'Contracts for Java' to define the constraints. import org.jetbrains.contract.Requires; import org.jetbrains.contract.Ensures; public class BankAccount { private double balance; public BankAccount(double initialBalance) { this.balance = initialBalance; } @Requires("amount > 0") @Ensures("balance >= old(balance)") public void deposit(double amount) { balance += amount; } @Requires("amount > 0 && amount <= balance") @Ensures("balance == old(balance) - amount") public void withdraw(double amount) { balance -= amount; } public double getBalance() { return balance; } } In the above examples, we used the prefix conditions and rear conditions of the method of `@reques` and@ENSURES` to define the method.`@Requires` Annotation is used to define the pre -factor conditions, which specifies the constraints of the passing parameters.`@ENSURES` Annotation is used to define the rear conditions, which specifies the constraints after the method execution. In the `DEPOSIT` method, we used the` @Requires ("amount> 0") to define the pre -conditions that must be greater than 0, and use the `@NSURES (" Balance> = OLD (BALANCE) ")))`To define the balance of the balance after the deposit must be greater than the rear conditions of the previous balance. Similarly, in the `withdraw` method, we used the` @Requires ("amount> 0 && amount <= Balance") `to define the front conditions that must be greater than 0 and less than equal to the balance, and use the We can also use the@invariant` annotation to define the class without variables. This is the constraints that must be maintained in the entire class. import org.jetbrains.contract.Invariant; @Invariant("balance >= 0") public class BankAccount { // ... } In the above example, we used the `@invariant (" Balance> = 0 ")` to define a class that must be greater than or equal to 0. By using the 'Contracts for Java' framework, we can express the constraints of the code more clearly and verify it during runtime.This helps us write more robust, maintenance and reliable Java code. Note: This case is only the purpose of demonstration. In the actual production environment, more complicated constraints and more comprehensive testing may be required.