面向对象例题

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
	}
}