Java第二周作业

1．编写一个程序，定义圆的半径,求圆的面积.

package homework2;

public class Text1 {

    /**
     * @param args
     */
    public static void main(String[] args) {
        int r=1;
        double area;
        area=3.14*r*r;
        System.out.println(area);

    }

}

2．华氏温度和摄氏温度互相转换

package homework2;

public class Text2 {

    /**
     * @param args
     */
    public static void main(String[] args) {
        double hua,she;
        hua=50;
        she=(hua-32)*5/9.0;
        System.out.println(she);
        she=30;
        hua=she*9.0/5+32;
        System.out.println(hua);

    }

}

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 homework2;

public class Text3 {

    /**
     * @param args
     */
    public static void main(String[] args) {
        int a=5;
          int b=8,c;
          c=a;
          a=b;
          b=c;
          System.out.println("a:"+a+"\nb:"+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 homework2;

public class Text4 {

    /**
     * @param args
     */
    public static void main(String[] args) {
        int a=12345,b;
        b=a/100*100;
        System.out.println(b);


    }

}

5．输入一个0～1000的整数，求各位数的和

package homework2;

public class Text5 {

    /**
     * @param args
     */
    public static void main(String[] args) {
        int a=123,sum;
        sum=(a%10)+(a%100/10)+(a%1000/100);
        System.out.println(sum);

    }

}

6．定义一个任意的大写字母A~Z，转换为小写字母

package homework2;

public class Text6 {

    /**
     * @param args
     */
    public static void main(String[] args) {
        char captial,result;
        captial='A';
        result=(char) (captial+32);
        System.out.println(result);
        
    }

}