一、简易计算器

使用静态方法模拟一个只能进行两个数加、减、乘、除的建议计算器。

package haha;
import java.util.Scanner;
public class Dog{   	
	public static double jia(double a,double b)
	{
		double c;
		c=a+b;
		return c;
	}
	
	public static double jian(double a,double b)
	{
		double c;
		c=a-b;
		return c;
	}
	
	public static double cheng(double a,double b)
	{
		double c;
		c=a*b;
		return c;
	}
	
	public static double chu(double a,double b)
	{
		double c;
		c=a/b;
		return c;
	}
	
	public static void main(String[] args)
	{
		Scanner sc=new Scanner(System.in);
		System.out.println("请输入两个数字，用空格隔开（a b）：");
		double a=sc.nextDouble();
		double b=sc.nextDouble();
		System.out.println(a+"加上"+b+"的结果："+jia(a,b));
		System.out.println(a+"减去"+b+"的结果："+jian(a,b));
		System.out.println(a+"乘上"+b+"的结果："+cheng(a,b));
		System.out.println(a+"除以"+b+"的结果："+chu(a,b));
	}
}

二、购买电影票

购买电影票有优惠：满十八周岁的付40元，未满十八周岁的享受半价。使用成员变量、成员方法、构造方法和this关键字，控制台输出如下所示的姓名、年龄票价等信息。

姓名年龄票价（元）

李明 20 40

钱丽 16 20

周刚 8 20

吴红 32 40

package haha;
public class Dog{   	
	String name;
	int age;
	int price;
	
	public Dog(String name,int age,int price) {
		this.name=name;
		this.age=age;
		this.price=price;
	}
	
	public static int Price(int age) {
		int price;
		if(age<18)
		{
			price=20;
		}
		else
		{
			price=40;
		}
		return price;
	}
	
	public static void main(String[] args) {
		System.out.println("姓名"+"    "+"年龄"+"    "+"票价（元）");
		Dog s1=new Dog("李明",20,Price(20));
		System.out.println(s1.name+"    "+s1.age+"    "+s1.price);
		Dog s2=new Dog("钱丽",16,Price(16));
		System.out.println(s2.name+"    "+s2.age+"    "+s2.price);
		Dog s3=new Dog("周刚",8,Price(8));
		System.out.println(s3.name+"    "+s3.age+"     "+s3.price);
		Dog s4=new Dog("吴红",32,Price(32));
		System.out.println(s4.name+"    "+s4.age+"    "+s4.price);
	}
}

三、计算平均分

使用成员变量、成员方法、构造方法和this关键字，先记录4名学生的语文、数学、英语这3科成绩，再计算每个人的平均分。运行结果如下：

学号姓名语文数学英语平均分

—————————————————————————————

1 张三 91.5 98.0 89.0 92.83333333333333

2 李四 96.0 98.5 93.0 95.83333333333333

3 王五 97.0 100.0 98.5 98.5

4 钱六 77.0 83.0 81.0 80.33333333333333

package haha;
public class Dog{   	
	String name;
	static int id=0;
	double chinese;
	double math;
	double english;
	
	public Dog(String name,double chinese,double math,double english) {
		this.name=name;
		this.chinese=chinese;
		this.math=math;
		this.english=english;
		id++;
	}
	
	public static double Avg(double chinese,double math,double english) {
		double avg=(chinese+math+english)/3;
		return avg;
	}
	
	public static void main(String[] args) {
		System.out.println("学号"+"      "+"姓名"+"        "+"语文"+"        "+"数学"+"        "+"英语"+"        "+"平均分");
		System.out.println("——————————————————————————————————————————————————————————————————————");
		Dog s1=new Dog("张三",91.5,98,89);
		System.out.println(s1.id+"        "+s1.name+"       "+s1.chinese+"       "+s1.math+"       "+s1.english+"       "+Avg(s1.chinese,s1.math,s1.english));
		Dog s2=new Dog("李四",96,98.5,93);
		System.out.println(s2.id+"        "+s2.name+"       "+s2.chinese+"       "+s2.math+"       "+s2.english+"       "+Avg(s2.chinese,s2.math,s2.english));
		Dog s3=new Dog("王五",97,100,98.5);
		System.out.println(s3.id+"        "+s3.name+"       "+s3.chinese+"       "+s3.math+"      "+s3.english+"       "+Avg(s3.chinese,s3.math,s3.english));
		Dog s4=new Dog("钱六",77,83,81);
		System.out.println(s4.id+"        "+s4.name+"       "+s4.chinese+"       "+s4.math+"       "+s4.english+"       "+Avg(s4.chinese,s4.math,s4.english));
	}
}

四、厘米与英寸互转

编写工具类，提供厘米与英寸之间的相互转换的工具方法。

package haha;
import java.util.Scanner;
public class Dog{   	
	public static double cmtoin(double a) {
		double b=0.393700788*a;
		return b;
	}
	
	public static double intocm(double a) {
		double b=2.5399999961392*a;
		return b;
	}
	
	public static void main(String[] args) {
		System.out.println("厘米转换成英寸请输入1，英寸转换为厘米请输入2：");
		Scanner sc=new Scanner(System.in);
		double n=sc.nextDouble();
		if(n==1)
		{
			System.out.println("请输入需要转换的厘米数：");
			double a=sc.nextDouble();
			System.out.println(a+"cm="+cmtoin(a)+"in");
		}
		else if(n==2)
		{
			System.out.println("请输入需要转换的英寸数：");
			double a=sc.nextDouble();
			System.out.println(a+"in="+intocm(a)+"cm");
		}
		else
		{
			System.out.println("输入无效！");
		}
	}
}