The best practical guide to the "Contracts for Java 'framework in the Java class library
The best practical guide to the "Contracts for Java 'framework in the Java class library
introduction:
When developing and designing the Java library, an excellent practice is to use Contracts to ensure the correctness, reliability and maintenance of the code.The 'Contracts for Java' framework provides a way to define the contract with pre -conditioning, rear conditions, and invariance.This article will introduce how to use the 'Contracts for Java' framework to create a high -quality Java class library and provide relevant best practical guidelines and examples.
First, why use the 'Contracts for Java' framework?
Using the contract can help us better understand and define the logic of code during the development process, thereby improving the quality and readability of the code.The 'Contracts for Java' framework provides a convenient way to create and use contracts. Its advantages include:
1. Easy to read and understand grammar: Using a contract with 'Contracts for Java' framework can intuitively define and understand the code, reducing the cognitive burden of developers.
2. Compulsory constraints: The use of frameworks can ensure that the code meets the contract requirements during runtime and avoid potential errors and abnormalities.
3. Improve the maintenance of code: Use a contract in the code makes the code easier to debug and maintain, and reduce the error spread of the code.
Second, the best practice of using 'Contracts for Java' framework
When using the 'Contracts for Java' framework, the following is the guidance principle of some best practice.
1. Use the right type of contract:
-Precondition: used to check the legality and correctness of the parameter or state.It is usually used to verify whether the input parameter meets specific conditions, such as parameter non -emptiness.
-PostConditions: The legitimacy of the verification method execution results.It is usually used to verify whether the return value meets the specific conditions.
-Invariants: used to limit the state of objects or classes to always meet specific conditions.
2. Use contracts at methods, constructors and class levels:
-Method level: Use the contract in the method signature to make appropriate restrictions on the passing parameters and the return value.
-The constructor level: Use the contract in the constructor to ensure that the creation and initialization of the object meet the specific conditions.
-ME level: Use the contract in the definition of the class to restrict the unchanged type of the class.
3. The arrangement and order of the contract:
-Fex conditions should be checked at the beginning of the method or constructor to ensure that the parameters before performing any operation are valid.
-The rear conditions should be checked at the end of the method or constructor to ensure that the return value or state meets specific conditions.
-Inval formula should be used in the method or constructor to ensure that the state of the object or class always meets specific conditions.
4. Clarify the contract and error message:
-The contract should be fully described so that developers and maintenance personnel can clearly understand their purpose and restrictions.
-The error message of the contract should be clear and clear, describing the specific reasons and location of the error.
5. Test contract with unit test: contract:
-In use unit tests to verify the correctness and effectiveness of the contract.
-In the unit test covering various situations, including border conditions and abnormal conditions.
3. Example:
Below is an example code that uses the 'Contracts for Java' framework to show how to use the contract in the Java library.
import org.contracts4j.Contract;
import org.contracts4j.ContractFactory;
import org.contracts4j.Predicate;
public class MathUtils {
private static final ContractFactory contractFactory = ContractFactory.getInstance();
public static int add(int a, int b) {
Contract contract = contractFactory.contract(MathUtils.class);
contract.precondition(new Predicate() {
public boolean eval() {
Return a> 0 && B> 0; // A and B should be greater than zero
}
});
contract.postcondition(new Predicate() {
public boolean eval() {
Return Contract.Result () == (a + b); // The method results should be equal to the sum of A and B
}
});
return a + b;
}
}
The above example shows a simple Mathutils class, where the ADD method uses the "Contracts for Java 'framework to define the contract.Precondition ensures that the parameters of the transmitted are greater than zero, and the return result of the PostCondition ensures that the return result of the method is equal to the sum of A and B.
in conclusion:
Use the 'Contracts for Java' framework in the Java class library to help improve the quality and readability of the code.This article introduces the best practical guide to use the framework, and provides a simple example code to demonstrate the use of the contract.Developers should actively adopt contracts when designing and developing the Java library, and combined with unit testing to verify their correctness.
