abstract class Student{   String name;   int fee;   Student(String name){       this.name=name;   }      abstract void setFee(int fee);   abstract int getFee();} interface Salary{    int getSalary();} class Graduate extends Student implements Salary{    int salary;    Graduate(String name){        super(name);    }    void setFee(int fee){        this.fee=fee;    }    int getFee(){        return fee;    }    public int getSalary(){        this.salary+=1500;        return salary;    }    boolean isLoan(){        if(salary-fee>0)            return false;        else return true;    }    }class Teacher implements Salary{    String name;    int salary;    Teacher(String name){        this.name=name;            }     public int getSalary(){        this.salary+=3000;        return salary;    }        }class University{    void payOff(Salary s){        s.getSalary();    }}public class Test{    public static void main(String args[]){        Graduate g=new Graduate("小梁");        g.setFee(1000);        University u =new University();        u.payOff(g);        System.out.println("是否需要贷款 "+g.isLoan());        Teacher t=new Teacher("大王");        u.payOff(t);    }}

课堂练习1：教材160页4.编程题

interface Animal{void cry();String getAnimalName();}class Simulator{    void playSound(Animal animal){        animal.cry();    }    void getAnimalName(Animal animal){        System.out.println(animal.getAnimalName());    }}class  Cat implements Animal{    String name="猫";    public void cry(){        System.out.println("猫");    }  public String getAnimalName(){    return this.name;}}class  Dog implements Animal{    String name="狗";    public void cry(){        System.out.println("狗");    }    public String getAnimalName(){    return this.name;}}public class Application{    public static void main(String args[]){        Simulator simulator=new Simulator();        simulator.playSound(new Dog());        simulator.playSound(new Cat());    }}