java第二次作业

1．编写一个程序，定义圆的半径,求圆的面积.

package exe2;

public class text3 {

    public static void main(String[] args) {
        // TODO Auto-generated method stub
        double r=3.0;
        double area=r*r*3.14;
        System.out.println("圆的面积="+area);
    }

}

2．华氏温度和摄氏温度互相转换

package exe2;

public class text {

    public static void main(String[] args) {
        // TODO Auto-generated method stub
        double hua=50,she=30;
        double she1=(hua-32)*5/9;
        double hua1=she*9/5+32;
        System.out.println(she1);
        System.out.println(hua1);


    }

}

3．已知a,b均是整型变量，写出将a,b两个变量中的值互换的程序。

package exe2;

public class text2 {

    public static void main(String[] args) {
        // TODO Auto-generated method stub
        int a=5,b=8,c;
        c=a;
        a=b;
        b=c;
        System.out.println("交换后的a:"+ a + ",b:" + b);
    }

}

4．定义一个任意的5位整数，将它保留到百位，无需四舍五入

package exe2;

public class text4 {

    
    public static void main(String[] args) {
        // TODO Auto-generated method stub
        int a=12345;
        int baiwei=(a/100)*100;
        System.out.println(baiwei);
        

    }

}

5．输入一个0～1000的整数，求各位数的和

package exe2;

public class text5 {


    public static void main(String[] args) {
        int zhengshu=234,sum;
        sum=(zhengshu%10)+(zhengshu%100/10)+(zhengshu%1000/100);
        System.out.println(sum);
        // TODO Auto-generated method stub

    }

}

6．定义一个任意的大写字母A~Z，转换为小写字母（知识点：变量和运算符综合应用）
   定义一个任意的小写字母a~z，转换为大写字母

package exe2;

public class text6 {

    public text6() {
        // TODO Auto-generated constructor stub
    }

    public static void main(String[] args) {
         char daxie,xiaoxie,shuchu;
         daxie='A';
         shuchu=(char) (daxie+32);
         System.out.println(shuchu);
         xiaoxie='a';
         shuchu=(char) (xiaoxie-32);
         System.out.println(shuchu);
        // TODO Auto-generated method stub

    }

}