1.电脑可以从U盘,数据相机,mp3等电子设备中下载数据

public class Computer {
USB usb;
}
public interface USB {
public void tran();
}
public class UDisk implements USB {
@Override
public void tran() {
System.out.println("U盘传数据。。");
}
}
public class Main {
public static void main(String[] args) {
Computer computer = new Computer();
UDisk uDisk = new UDisk();
computer.usb = uDisk;
computer.usb.tran();
}
}
2.班级由多个学生和只有一个教师组成;(更改老师,添加,删除学生)

public class Classes {
String name;
Student[] students;
Teacher teacher;
}
public class Student {
String name;
}
public class Teacher {
String name;
}
public class Main {
public static void main(String[] args) {
Classes classes = new Classes();
classes.name = "一年一班";
Teacher teacher = new Teacher();
teacher.name="tom";
Student s1 = new Student();
s1.name = "jack";
Student s2 = new Student();
s1.name = "rose";
classes.teacher = teacher;
classes.students = new Student[2];
classes.students[0] = s1;
classes.students[1] = s2;
System.out.println(classes.teacher.name);
for(int i = 0;i<classes.students.length;i++){
System.out.println(classes.students[i].name);
}
Teacher t1 = new Teacher();
t1.name = "king";
classes.teacher = t1;
classes.students[1] = null;
Student s3 = new Student();
s3.name = "allia";
classes.students[1] = s3;
}
}
模拟一下开心牧场;农场中有农户,各种动物(牛,马,羊,鸡等),农户可以喂养动物;

public class Farm {
Farmer[] farmers;
}
ublic class Farmer {
String name;
Animal[] animals;
public void feed(){
for(int i = 0;i<animals.length;i++){
animals[i].eat();
}
}
}
public class Animal {
public void eat(){
}
}
public class Cow extends Animal{
@Override
public void eat() {
System.out.println("牛吃草");
}
}
public class Horse extends Animal{
@Override
public void eat() {
System.out.println("马吃草");
}
}
public class Main {
public static void main(String[] args) {
Farm farm = new Farm();
Farmer farmer = new Farmer();
farmer.name = "张三";
Cow cow = new Cow();
Horse horse = new Horse();
farmer.animals = new Animal[]{cow,horse};
farm.farmers = new Farmer[]{farmer};
farm.farmers[0].feed();
}
}