Demo :: Composition over Inhertiance

Employee.java

abstract class Employee {
    public int id;
    
    public abstract void accept(EmployeeVisitor employeeVisitor);
}

class HourEmployee extends Employee {
    
    @Override
    public void accept(EmployeeVisitor employeeVisitor) {
        employeeVisitor.visit(this);
    }
}

class SalaryEmployee extends Employee{
    @Override
    public void accept(EmployeeVisitor employeeVisitor) {
        employeeVisitor.visit(this);
    }
}

EmployeeVisitor.java

interface EmployeeVisitor {
    void visit(HourEmployee hourEmployee);
    void visit(SalaryEmployee salaryEmployee);
}

first.java

abstract class Employee {
    public abstract String generateReport();
}

class HourEmployee extends Employee {

    @Override
    public String generateReport() {
        return null;
    }
}

class SalaryEmployee extends Employee{

    @Override
    public String generateReport() {
        return null;
    }
    
}

HourReport.java

class HourReport implements EmployeeVisitor {

    public void visit(HourEmployee hourEmployee) {
        System.out.println("Report of hour employee : " +  hourEmployee.id);
    }

    public void visit(SalaryEmployee salaryEmployee) {
        
    }
    
}

Use.java

HourReport hourReport = new HourReport();
employees.stream().forEach(p->p.accept(hourReport));


## ผลลัพธ์ ##
Report of hour employee : 1
Report of hour employee : 2