CS99

Lab 3: Solutions

Lab3.java

import java.io.*;

/**  * CS99 Lab 3  
* Author: your name here  
* NetID: your NetID here  
* Date: today's date  
*/
class Lab3 {   
    public static void main( String[] args ) {       
        TokenReader in = new TokenReader( System.in );       
        System.out.print("Enter an integer value : ");       
        double firstVal = in.readDouble();       
        System.out.print("Enter a second integer value : ");       
        double secondVal = in.readDouble();       
        System.out.print("The sum of the values is " + ( firstVal + secondVal) );       
        System.out.println("; their difference is " + ( firstVal - secondVal) + ";" );       
        System.out.print("their product, " + ( firstVal*secondVal) );       
        System.out.println("; and their quotient, " + ( firstVal/secondVal) + "." );   
    }
}

Lab3.TXT

Part A:
Enter an integer value : 31
Enter a second integer value : 12
The sum of the values is 43; their difference is 19;
their product, 372; and their quotient, 2.

Why does the quotient return 0 if firstVal is 7, and secondVal is 8? 
The quotient is zero because we are performing integer division, and the return value must be an integer.  Since 7/8 is not an integer and is less than 1, Java returns the next smallest integer, which is 0.
What does it return if firstVal is 8 and secondVal is 7? 
In this case, the next smallest integer is 1, because 8/7 is just a little greater than 1.

Part B:
Enter a double value : 2.71828
Enter a second double value : 3.14159
The sum of the values is 5.85987; their difference is -0.42330999999999985;
their product, 8.539721265199999; and their quotient, 0.8652561282662601.

Part C:
The program does not compile because the computer does not know how to take the difference, product, and quotient of Strings.

Error   : Incompatible type for -. Can't convert java.lang.String to int.
Lab3.java line 17     System.out.println("; their difference is " + ( firstVal - secondVal) + ";" );

Note: Depending on how you wrote your program, you may have gotten a different error.

Part D:
Enter a String value : Banana
Enter a second String value :  Bread
The sum of the Strings is BananaBread.

class TaxiFare {

   public static void main( String[] args ) {
       TokenReader in = new TokenReader( System.in );
       System.out.print("Enter a distance (in miles): " );
       double distance = in.readDouble();
       double fare = 5 + 2*(Math.ceil ( 8*distance ) - 1);
       System.out.println("The taxi fare is " + fare + " dollars." );
   }
 
}

class TimeConv {

   public static void main( String[] args ) {
       TokenReader in = new TokenReader( System.in );
       System.out.print("Enter a time (in seconds): " );
       int time = in.readInt();
       int hours = time/3600;
       int minutes = (time%3600)/60;
       int seconds = (time%3600)%60;
       System.out.println(time + " seconds equals " + hours + " hours, " + minutes +
           " minutes, and " + seconds + " seconds." );
   }
 
}