Exercise (Solutions)

E1

What is wrong with the following variable declarations?

int x = “24”;
boolean isFun = “true”;
String myname = jayshree;
int my number;
int 24_number = 24;

E2

In the below program, you want all the additions to be evaluated first before multiplication and division can happen. How do you fix the code to make that happen?

class MyClass {


    public static void main(String[]args) {
        double d = 5 * 6 + 4 + 5 / 3;
        System.out.println(d);
    }
}

E3

What is wrong with the below code?

class MyClass {

    public static void main(String[]args) {
        b = 10;
        System.out.println(b);
    }
}

E4

Write a program that prints out the name, street name, city, phone number all on different lines by taking all the inputs from Scanner one at a time.

E5

The program below is supposed to calculate and show the time it takes for light to travel from the sun to the earth. When you run the program it prints 0 min and -1 sec as the time, which makes no sense. Fix the program so that it will show the correct value of 8 minutes and 20 secs:

public class SunLightTimer {


    public static void main(String[] args) {

            int earthDistanceFromSunInKm = 150000000;
            int speedOfLightInMetersPerSec = 299792458;

            //Convert distance to meters:
            int earthDistanceFromSunInMeters = earthDistanceFromSunInKm * 1000;
            int timeTakenByLightInSecs = earthDistanceFromSunInMeters / speedOfLightInMetersPerSec;
            System.out.println(timeTakenByLightInSecs + " secs");

            int timeInMins = timeTakenByLightInSecs / 60;
            timeTakenByLightInSecs = timeTakenByLightInSecs - (timeInMins * 60);
            System.out.println("Light will take.. ");
            System.out.println(timeInMins + " minute(s) and " + timeTakenByLightInSecs + " second(s)");
            System.out.println("to reach earth from sun ");
        }
}

E6

Write a console program to define and initialize a variable of type byte to 1 and then successively multiply it by 2 and display its value 8 times. Observe the output and explain the reason for the displayed value in the last output.

Here is the partial code given:

byte a = 1;
a  *= 2;
System.out.println(a);

Repeat the second and third line 8 times and explain the value that you see in the last output statement.