某学校教师每月工资的计算公式如下：固定工资+课时补贴。教授的固定工资为5000元，每个课时补贴50元：副教授的固定工资为 3000元，每个课时补贴30元；讲师的固定工资为2000元，每个课时补贴20元。定义教师抽象类，派生不同职称的教师子类，编写程序求若干教师的月工资

为了实现这个需求，我们可以定义一个名为`Teacher`的抽象类，包含固定的`salary`属性和一个计算月工资的方法`calculateMonthlySalary`。然后分别创建`Professor`, `AssociateProfessor`, 和 `AssistantProfessor` 这些具体的子类，并覆盖父类的计算方法，反映各自的固定工资和课时补贴。

首先，定义`Teacher`类：

public abstract class Teacher {
    private int fixedSalary;
    private double hourBonus;

    public Teacher(int fixedSalary, double hourBonus) {
        this.fixedSalary = fixedSalary;
        this.hourBonus = hourBonus;
    }

    // 抽象方法，需要子类提供实现
    public abstract double calculateHourlyBonus();

    // 计算月工资的方法
    public double calculateMonthlySalary(int teachingHours) {
        return fixedSalary + teachingHours * calculateHourlyBonus();
    }
}

接着，创建子类并实现`calculateHourlyBonus()`方法：

public class Professor extends Teacher {
    public Professor() {
        super(5000, 50);
    }

    @Override
    public double calculateHourlyBonus() {
        return 50;
    }
}

public class AssociateProfessor extends Teacher {
    public AssociateProfessor() {
        super(3000, 30);
    }

    @Override
    public double calculateHourlyBonus() {
        return 30;
    }
}

public class AssistantProfessor extends Teacher {
    public AssistantProfessor() {
        super(2000, 20);
    }

    @Override
    public double calculateHourlyBonus() {
        return 20;
    }
}

现在你可以实例化这些教师，并调用他们的`calculateMonthlySalary`方法来获取工资，比如：

public static void main(String[] args) {
    Professor professor = new Professor();
    double profSalary = professor.calculateMonthlySalary(20); // 教授20课时的工资

    AssociateProfessor associateProfessor = new AssociateProfessor();
    double assocSalary = associateProfessor.calculateMonthlySalary(30); // 副教授30课时的工资

    AssistantProfessor assistantProfessor = new AssistantProfessor();
    double asstSalary = assistantProfessor.calculateMonthlySalary(40); // 讲师40课时的工资

    System.out.println("Professor salary: " + profSalary);
    System.out.println("Associate Professor salary: " + assocSalary);
    System.out.println("Assistant Professor salary: " + asstSalary);
}