代码语言：javascript复制
// Bad example without SRP
class Employee {
private String name;
private int id;
private int salary;
public Employee(String name, int id, int salary) {
this.name = name;
this.id = id;
this.salary = salary;
}
public void calculateSalary() {
// Complex calculation based on employee's type, experience, etc.
// ...
}
public void save() {
// Save employee data to database
// ...
}
public void sendEmail() {
// Send email to employee
// ...
}
}
// Good example with SRP
class Employee {
private String name;
private int id;
private int salary;
public Employee(String name, int id, int salary) {
this.name = name;
this.id = id;
this.salary = salary;
}
public int calculateSalary() {
// Complex calculation based on employee's type, experience, etc.
// ...
return salary;
}
}
class EmployeeDAO {
public void save(Employee employee) {
// Save employee data to database
// ...
}
}
class EmailService {
public void sendEmail(Employee employee) {
// Send email to employee
// ...
}
}在这个例子中，我们定义了一个Employee类，它负责保存员工的姓名、工号和薪水，并且实现了三个方法：calculateSalary、save和sendEmail。
在不遵循SRP原则的情况下，Employee类承担了太多的职责：它既要计算员工的薪水，还要保存员工的数据，还要发送邮件给员工。这样，Employee类的代码变得非常复杂，难以维护和修改，而且不利于代码的重用和测试。
为了遵循SRP原则，我们可以将Employee类拆分成三个单一职责的类：Employee、EmployeeDAO和EmailService。其中，Employee类只负责保存员工的姓名、工号和薪水，而calculateSalary方法则被移到Employee类中，以计算员工的薪水。EmployeeDAO类负责保存员工的数据到数据库中，而EmailService则负责向员工发送邮件。这样，每个类都只承担了自己的职责，代码变得更加清晰和易于理解，而且有利于代码的重用和测试。
