1 class A 2 { 3 final int f=10; 4 double d; 5 abstract void method(); 6 }

这段代码定义了一个抽象类A，包含一个final修饰的int类型变量f、一个double类型变量d和一个抽象方法method()。final修饰的变量f表示该变量的值不能被修改，因此在类A中定义时必须进行初始化。

需要注意的是，抽象类中的抽象方法没有具体的实现，因此不能直接创建抽象类的实例。如果要使用抽象类中的方法，必须通过继承该抽象类并实现其中的抽象方法来创建一个子类。例如：

abstract class A {
    final int f = 10;
    double d;
    abstract void method();
}

class B extends A {
    void method() {
        System.out.println("This is a method in B");
    }
}

public class E {
    public static void main(String args[]) {
        A a = new B();
        a.method(); // 输出"This is a method in B"
    }
}

在这个例子中，B类继承了A类，并实现了其中的抽象方法method()。在主函数中，创建了一个B类的实例并将其向上转型为A类型，通过A类型的变量来调用method()方法，输出了一段信息。

相关问题

把public abstract class Employee { protected String name; // 姓名 protected double fixedSalary; // 固定工资 public Employee(String name, double fixedSalary) { this.name = name; this.fixedSalary = fixedSalary; } // 计算月工资的抽象方法 public abstract double calculateSalary(int overtime);}和public class SeniorEngineer extends Employee { private static final double OVERTIME_SUBSIDY = 50.0; public SeniorEngineer(String name) { super(name, 5000.0); } @Override public double calculateSalary(int overtime) { return fixedSalary + overtime * OVERTIME_SUBSIDY; }}public class JuniorEngineer extends Employee { private static final double OVERTIME_SUBSIDY = 30.0; public JuniorEngineer(String name) { super(name, 3000.0); } @Override public double calculateSalary(int overtime) { return fixedSalary + overtime * OVERTIME_SUBSIDY; }}public class Trainee extends Employee { private static final double OVERTIME_SUBSIDY = 20.0; public Trainee(String name) { super(name, 2000.0); } @Override public double calculateSalary(int overtime) { return fixedSalary + overtime * OVERTIME_SUBSIDY; }}和public class Main { public static void main(String[] args) { Employee[] employees = { new SeniorEngineer("张三"), new JuniorEngineer("李四"), new Trainee("王五") }; int[] overtimes = {10, 20, 30}; for (int i = 0; i < employees.length; i++) { double salary = employees[i].calculateSalary(overtimes[i]); System.out.println(String.format("%s的月工资为：%.2f元", employees[i].name, salary)); } }}合成一个程序

public abstract class Employee {
protected String name; // 姓名
protected double fixedSalary; // 固定工资

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

// 计算月工资的抽象方法
public abstract double calculateSalary(int overtime);
}

public class SeniorEngineer extends Employee {
private static final double OVERTIME_SUBSIDY = 50.0;

public SeniorEngineer(String name) {
super(name, 5000.0);
}

@Override
public double calculateSalary(int overtime) {
return fixedSalary + overtime * OVERTIME_SUBSIDY;
}
}

public class JuniorEngineer extends Employee {
private static final double OVERTIME_SUBSIDY = 30.0;

public JuniorEngineer(String name) {
super(name, 3000.0);
}

@Override
public double calculateSalary(int overtime) {
return fixedSalary + overtime * OVERTIME_SUBSIDY;
}
}

public class Trainee extends Employee {
private static final double OVERTIME_SUBSIDY = 20.0;

public Trainee(String name) {
super(name, 2000.0);
}

@Override
public double calculateSalary(int overtime) {
return fixedSalary + overtime * OVERTIME_SUBSIDY;
}
}

public class Main {
public static void main(String[] args) {
Employee[] employees = {
new SeniorEngineer("张三"),
new JuniorEngineer("李四"),
new Trainee("王五")
};
int[] overtimes = {10, 20, 30};
for (int i = 0; i < employees.length; i++) {
double salary = employees[i].calculateSalary(overtimes[i]);
System.out.println(String.format("%s的月工资为：%.2f元", employees[i].name, salary));
}
}
}

设计一个抽象类名字为 Person,它的子类为Student和 Employee；person类有name以及toString方法；student有 status属性(freshman, sophomore, junior, or senior),定义status 为常量;Employee类 有office, salary；分别定义各个类的有参构造方法，Person(String name)、Student（String name,int status）、Employee(String name,String office,double salary),注意需要在子类构造方法第一句调用父类有参构造方法，为子类也实现toString方法。编写测试类定义一个数组存放每个非抽象类对象（Student和 Employee），然后利用多态调用toString方法打印各个对象的所有属性信息。(为了减少书写量，只需要为name属性完成get和set方法，其他属性不用写)

以下是根据您的要求设计的Person抽象类及其子类Student和Employee的Java代码：

abstract class Person {
    protected String name;

    public Person(String name) {
        this.name = name;
    }

    public abstract String toString();

    public String getName() {
        return name;
    }

    public void setName(String name) {
        this.name = name;
    }
}

class Student extends Person {
    private int status;
    public static final int FRESHMAN = 1;
    public static final int SOPHOMORE = 2;
    public static final int JUNIOR = 3;
    public static final int SENIOR = 4;

    public Student(String name, int status) {
        super(name);
        this.status = status;
    }

    @Override
    public String toString() {
        return "学生姓名: " + name + ", 学生状态: " + getStatusName();
    }

    private String getStatusName() {
        switch (status) {
            case FRESHMAN:
                return "一年级";
            case SOPHOMORE:
                return "二年级";
            case JUNIOR:
                return "三年级";
            case SENIOR:
                return "四年级";
            default:
                return "未知";
        }
    }
}

class Employee extends Person {
    private String office;
    private double salary;

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

    @Override
    public String toString() {
        return "员工姓名: " + name + ", 员工办公室: " + office + ", 员工薪水: " + salary;
    }
}

public class Test {
    public static void main(String[] args) {
        Person[] people = new Person[2];
        people[0] = new Student("张三", Student.SOPHOMORE);
        people[1] = new Employee("李四", "A101", 5000.0);

        for (Person person : people) {
            System.out.println(person.toString());
        }
    }
}

在这个程序中，定义了抽象类Person，其中包含了name属性和toString方法。Student类和Employee类分别继承自Person类，并添加了各自的属性和相关方法。在子类的构造方法中，通过super关键字调用了父类的有参构造方法。

测试类Test创建了一个Person类型的数组，用于存放Student和Employee对象。通过多态性，遍历数组并调用toString方法打印出每个对象的所有属性信息。

希望这个程序满足了您的需求！如果还有其他问题，请随时提问。