定义抽象类和接口Pet和CanCry, 再定义Dog和Cat分别同时继承Pet和实现CanCry,
接口中定义方法scream
Pet中含有抽象方法run, 分别调用在控制台上打印不同的内容
public class Dog extends Pet implements CanCry {
@Override
public void Scream() {
System.out.println("汪汪");
}
@Override
public void run() {
System.out.println("撒腿跑");
}
}
public class Cat extends Pet implements CanCry{
@Override
public void Scream() {
System.out.println("喵喵");
}
@Override
public void run() {
System.out.println("上树");
}
}
public abstract class Pet {
public abstract void run ();
}
public interface CanCry {
public void Scream();
}
Pet dog = new Dog(); //父类的引用指向子类 CanCry c = new Dog(); dog.run(); c.Scream();
编写一个计算时间类MyTime, 含有属性时分秒, 声明两个构造方法, 空参和带参数的,
可以分别实例化一个默认的时间0:0:0和一个指定的时间,
再提供可以分别修改时分秒的三个方法,
可以修改时间为某个时间段之前或之后的时间
public class MyTime {
private int hour;
private int minutes;
private int seconds;
public MyTime() {}
public MyTime(int hour, int minutes, int seconds) {
super();
this.hour = hour;
this.minutes = minutes;
this.seconds = seconds;
}
public void changeMinute(int a) {
this.setMinutes(this.getMinutes()+a);
}
public void changeHour(int b) {
this.setHour(this.getHour()+b);
}
public void changeSecond(int c) {
this.setMinutes(this.getSeconds()+c);
}
public int getHour() {
return hour;
}
public void setHour(int hour) {
this.hour = hour;
}
public int getMinutes() {
return minutes;
}
public void setMinutes(int minutes) {
this.minutes = minutes;
}
public int getSeconds() {
return seconds;
}
public void setSeconds(int seconds) {
this.seconds = seconds;
}
@Override
public String toString() {
return "当前时间: [" + hour + ":" + minutes + ":" + seconds + "]";
}//重写,返回的是字符串
}
MyTime time2 = new MyTime(11,25,20); System.out.println(time2);//系统会默认执行ToString的方法 time2.changeHour(5); time2.changeMinute(10); time2.changeSecond(20); System.out.println(time2);
效果如下图:
编写父类Animals, 子类Dog, Cat, 统计实例化的数量,
即总共有多少只, Dog多少只, Cat多少只, 某一只动物是第几只
public class Animals { //父类
private String name;
public static int num;
public Animals() {}
public Animals(String name) {
num++; //为了让其显示动物的个数
this.name = name;
}
public String getName() {
return name;
}
public void setName(String name) {
this.name = name;
}
}
public class Dog extends Animals { //子类
public static int dogNum;
private int y;
public Dog() {}
public Dog( String name) {
super(name);
dogNum++;
setY(dogNum);
}
public static int getDogNum() {
return dogNum;
}
public static void setDogNum(int dogNum) {
Dog.dogNum = dogNum;
}
public int getY() {
return y;
}
public void setY(int y) {
this.y = y;
}
}
public class Cat extends Animals { //子类
public static int catNum;
private int x; //给其一个属性接收catNum,同时set,get一下,同理在Dog里也可以实现
public Cat() {}
public Cat( String name) {
super(name);
catNum++;
setX(catNum);
}
public static int getCatNum() {
return catNum;
}
public static void setCatNum(int catNum) {
Cat.catNum = catNum;
}
public int getX() {
return x;
}
public void setX(int x) {
this.x = x;
}
}
Dog a1 = new Dog("小花");
Cat a2 = new Cat("小白");
Dog a3 = new Dog("小黑");
Cat a4 = new Cat("小壮");
System.out.println("总共有"+Animals.num+"只动物");
System.out.println("总共有"+Dog.dogNum + "只狗"+","+Cat.catNum+"只猫");
System.out.println(a1.getName()+"是第"+a1.getY()+"只狗");
System.out.println(a4.getName()+"是第"+a4.getX()+"只猫");
编写一个平面几何图形Shape抽象类, 提供计算面积的方法, 再定义Rectangle矩形类和Circle类, 分别继承
Shape类, 使用不同的方法计算面积
public abstract class Shape { //抽象类
public abstract void getarea() ;
}
public class Circle extends Shape { //继承
private int radious;
public Circle() {}
public Circle(int radious) {
super();
this.radious = radious;
}
@Override
public void getarea() {
double s = Math.PI*radious*radious;
System.out.println("圆的面积" + s);
}
}
public class Rectangle extends Shape {//继承
private int kuan;
private int chang;
public Rectangle() {}
public Rectangle(int kuan, int chang) {
super();
this.kuan = kuan;
this.chang = chang;
}
@Override
public void getarea() {
double s = kuan*chang;
System.out.println("矩形的面积"+ s);
}
}
Shape x = new Circle(5); Shape y = new Rectangle(5,7); x.getarea(); y.getarea();
猜数字, 编写一个类, 实例化的时候会初始化某个属性, 给一个1-10的随机数,
使用Scanner输入猜数字是多少
出现效果如下图所示:
try catch 捕获异常的体现:
import java.util.Random;
public class GussNumber {
private int num; //初始化
public GussNumber() { //构造的方法
System.out.println("请输入数字...");
this.setNum(getRandom());//默认的数字就是随机数取出来的数字
}
public int getRandom() { //给了一个有返回值的方法
Random r = new Random();
int i = r.nextInt(10)+1; //取1到10的随机数
return i;
}
public boolean isRight(int num) { //给一个布尔值的又返回类型的方法,判断
boolean f= false;
if( this.num == num) {
System.out.println("猜对了");
f = true;
}else if (this.num > num) {
System.out.println("小了");
}else if (this.num < num) {
System.out.println("大了");
}
return f;
}//输对了返回一个true,输错了返回一个false
public int getNum() {
return num;
}
public void setNum(int num) {
this.num = num;
}
}
import java.util.Scanner;
public class Main {
public static void main(String[] args) {
GussNumber gn = new GussNumber();
Scanner scanner = new Scanner(System.in);
boolean flag = true;
while(flag) { //while循环的目的是,如果数字输错了的话,可以继续输入
String s = scanner.nextLine(); //等着输入
try {
int x = Integer.parseInt(s);//使输入的内容强转成int型
flag = !gn.isRight(x);//判断输入的内容是否正确,用!的意思是说,如果 是true(输入正确)的话
//,取反,是false,程序不再运行
} catch (NumberFormatException e) {
System.out.println("请输入数字..");
} //用try,catch的目的是捕获异常,如果输入的不是数字的话,就会报错
}
scanner.close(); //控制台关闭
}
}