EQUALSVERIFIER | Release Normal Jar framework in the Java Library's technical principles
EQUALSVERIFIER is an open source library for Java libraries to help developers to achieve high -quality Equals and HashCode methods.It provides a simple, reliable and easy -to -use way to verify the correctness and performance of the Equals and HashCode methods.This article will study the technical principles of Equalsverifier in the Java class library and provide the corresponding Java code example.
1 Overview:
Generally, when we customize Equals and Hashcode methods in the Java class, we must follow some important agreement and rules.In this regard, Equalsverifier uses technical principles such as reflexes and generating objects to simplify this process so that developers can easily check whether these methods can correctly implement the equal nature and hash code specifications.
2. EQUALSVERIFIER core principle:
The core principles of EQUALSVERIFIER involve the following key steps:
2.1 Create the object to be tested
EQUALSVERIFIER uses ObjectAccessor to create objects to be tested.This object generator is an important part of Equalsverifier. It creates an instance object through reflection and access to private structure functions and other technologies for subsequent equalization and hash code verification.
2.2 Verification Equals method:
EQUALSVERIFIER first verifies the EQUALS method to ensure that it meets equal standards.It creates two equal instance objects, and then compares their other fields to achieve verification.Specifically, Equalsverifier will verify the following points:
-Huyanity: If object A is equal to object B, the object B is also equal to Object A.
-Forne: That is, the same object should be equal to himself.
-Profitability: If object A is equal to object B, and object B and object C are equal, the object A is equal to object C.
-Sipinity: When the object is not modified, the results of calling the EQUALS method multiple times should be consistent.
2.3 Verification HashCode method:
EQUALSVERIFIER next verifies the HashCode method to ensure that it correctly calculates the hash code value.For this reason, it first check whether the instance object has equal hash code, and then the unknown instance object has a variety of hash code.In this process, Equalsverifier uses many object instances and hash codes to ensure the correctness of the HashCode method.
3. Use examples:
The following is an example of EqualSverifier in the Java library:
import nl.jqno.equalsverifier.EqualsVerifier;
import nl.jqno.equalsverifier.Warning;
public class MyClass {
private int id;
private String name;
public MyClass(int id, String name) {
this.id = id;
this.name = name;
}
// equals and hashCode methods
@Override
public boolean equals(Object obj) {
if (this == obj) {
return true;
}
if (obj == null || getClass() != obj.getClass()) {
return false;
}
MyClass other = (MyClass) obj;
return id == other.id && name.equals(other.name);
}
@Override
public int hashCode() {
return Objects.hash(id, name);
}
public static void main(String[] args) {
EqualsVerifier.forClass(MyClass.class)
.suppress(Warning.NONFINAL_FIELDS)
.verify();
}
}
In the above example, we define a simple MyClass class and implement the Equals and HashCode methods.In the main method, we use the EQUALSVERIFIER.FORCLASS method to create an EQUALSVERIFIER instance and specify a class to be verified.We then ignore some warnings using the .suppress method, such as the warning of the non -final field.Finally, we call the.verify method to perform verification operations.
Through the above code examples and explanations, we understand the technical principles of Equalsverifier in the Java library.It can be seen that Equalsverifier realizes a simple and reliable method by reflecting and generating objects to verify the correctness and performance of Equals and HashCode methods.This enables developers to better ensure the equal nature of the objects in their Java class libraries and the accuracy of hash code.
