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, one at a time from the user, using Scanner.

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 when run:

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");

        printTimeInMinSec(timeTakenByLightInSecs);

    }

    public static void printTimeInMinSec(int sec){
        int min = sec/60;
        sec = sec - (min * 60);
        System.out.println("Light will take.. ");
        System.out.println(min + " minute(s) and " + sec + " 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.

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