设计模式之单一职责模式

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// 单一职责模式顾名思义就是一个类尽量保证只有一个职责。比如生活中相机只用来拍照、MP3只用来听歌。当我们把这些功能如果放在一起的话 就会变得很复杂。代码也一样 会导致代码维护困难。牵一发而动全身。
// 手机的发展有他自己的特点：然而编程时，我们却是要在类的职责分离上多思考，做到单一职责，这样的代码才是真正的以维护、易扩展、易复用、灵活多样。

例子

员工薪资计算

// 构建一个员工类

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public class Employee {
    private String id;
    private String name;
    private double salary;

    public Employee(String id, String name, double salary) {
        this.id = id;
        this.name = name;
        this.salary = salary;
    }

    // Getters and setters
    public String getId() {
        return id;
    }

    public String getName() {
        return name;
    }

    public double getSalary() {
        return salary;
    }

    public void setSalary(double salary) {
        this.salary = salary;
    }
}

// 员工数据管理类

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public class EmployeeDAO {
    private List<Employee> employees = new ArrayList<>();

    public void addEmployee(Employee employee) {
        employees.add(employee);
    }

    public void removeEmployee(String id) {
        employees.removeIf(employee -> employee.getId().equals(id));
    }

    public Employee findEmployee(String id) {
        return employees.stream()
                .filter(employee -> employee.getId().equals(id))
                .findFirst()
                .orElse(null);
    }
}

// 薪资计算类

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public class SalaryCalculator {
    public double calculateMonthlySalary(Employee employee) {
        // 这里可以加入更复杂的薪资计算逻辑
        return employee.getSalary();
    }

    public double calculateYearlySalary(Employee employee) {
        return employee.getSalary() * 12;
    }
}

// 员工报告生成类

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public class EmployeeReporter {
    public String generateReport(Employee employee) {
        return "Employee Report:\n" +
                "ID: " + employee.getId() + "\n" +
                "Name: " + employee.getName() + "\n" +
                "Salary: $" + employee.getSalary();
    }
}

// main函数（主类）

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public class EmployeeManagementSystem {
    public static void main(String[] args) {
        Single.EmployeeDAO dao = new Single.EmployeeDAO();
        Single.SalaryCalculator calculator = new Single.SalaryCalculator();
        Single.EmployeeReporter reporter = new Single.EmployeeReporter();

        // 添加员工
        Single.Employee john = new Single.Employee("E001", "John Doe", 5000);
        dao.addEmployee(john);

        // 计算薪资
        double monthlySalary = calculator.calculateMonthlySalary(john);
        System.out.println("John's monthly salary: $" + monthlySalary);

        // 生成报告
        String report = reporter.generateReport(john);
        System.out.println(report);
    }
}