JAVA练习题1（初级）

1.求一光年是多少千米 , 光在真空中传播速度299792458 m/s

public class demo01 {
   
    
    public static void main(String[] args) {
   
        long time = 60*60*24*365;
        long lon = (299792458*time)/1000;
        System.out.println("一光年："+lon+"千米");
            
    }
}

2.根据天数（46）计算周数和剩余的天数

public class demo02 {
   
    public static void main(String[] args) {
   
        int day = 46;
        int week = day/7;
        int surplusday = day%7;
        System.out.println("周数为："+week);
        System.out.println("剩余天数:"+surplusday);
    }
}

3.已知圆的半径radius= 1.5，求其面积 (Java中π用Math.PI表示)

public class demo03 {
   
    public static void main(String[] args) {
   
        double pi = Math.PI;
        double radius = 1.5;
        double area = pi*Math.pow(radius,2);
        System.out.println("该圆形的面积为:"+area);
    }
}

4. 自己给定5个整数，通过编程求出最大值(使用三元运算符)

public class demo04 {
   
   
    public static void main(String[] args) {
   
         int a = 10,b= 20,c = 30,d = 40,e = 50;
         int max = (a>b)?a:b;
          max = (max>c)?max:c;
          max = (max>d)?max:d;
          max = (max>e)?max:e;
        System.out.println(max);

    }
}

5. 韩梅梅看中两把价格相同的扇子，想挑选一个扇面较大的扇子购买，请你帮她挑选。

   ​ A款折叠扇：展开后角度为134.6°,扇骨长26.5cm
   ​ B款圆扇：扇柄长12.3cm，扇子总长度36.5cm
   ​ 注：圆形面积 = 3.14 * 半径平方
   ​ 扇形面积 = 3.14 * 半径平方 * (度数/360)

public class demo05 {
   
    public static void main(String[] args) {
   

        double a = 3.14*Math.pow(26.5,2)*(134.6/360);
        double blong = ((36.5-12.3)/3.14)/2;
        double b = 3.14*Math.pow(blong,2);
        System.out.println("扇面较大的为:"+((a>b)?"折叠扇":"圆扇"));
    }
}

6.变量a和b的值互换 例如：int a = 10,b=20; 结果：a=20,b=10;

public class demo06 {
   
    public static void main(String[] args) {
   
        int a = 10;
        int b = 20;
        System.out.println("互换前a:"+a+"\tb:"+b);
        int temp = a;
        a = b;
        b = temp;
        System.out.println("互换前a:"+a+"\tb:"+b);
    }
}

7.定义一个变量，是一个三位数，求各个位数的和. 如：123，结果是1+2+3=6

public class demo07 {
   
    public static void main(String[] args) {
   
        int num = 123;
        int a = num / 100;
        int b = num / 10 % 10;
        int c = num % 10;
        System.out.println("结果是:" + (a + b + c));
    }
}