Chapter 1:  "Java Foundamentals"

Data Structures with Java, Rick Mercer

Answers to Self-Check Questions


1-1 - either "valid" or explanation of why not "valid"
	  -a- valid
	  -b- identifier cannot begin with a number
	  -c- valid
	  -d- identifier cannot contain a period (dot)	
	  -e- cannot contain a space 
	  -f- valid
	  -g- cannot contain '(' or ')'
	  -h- valid
	  -i- cannot contain periods (dots)
	  -j- valid, but reserved
	  -k- cannot begin with a number
	  -l- cannot contain a space
	  -m- valid
	  -n- valid
	  -o- cannot contain a back slash (special character)
	  -p- valid (and it exists in several places in Java's libriaries)
	
1-2 valid or not valid
	  -a- valid
	  -b- not valid
	  -c- not valid
	  -d- valid

1-3 

import java.util.Scanner;

public class RelativeError {
	public static void main (String[]args){
		double relativeError=0.0;
		Scanner keyboard = new Scanner(System.in);
		System.out.println("Enter relativeError [0.0 through 1.0]: ");
		relativeError = keyboard.nextDouble();
		System.out.println("You entered: " + relativeError);
	}
}


1-4  4.6
     -2.2
     4.08
     0.35  let 2 decimals be enough, actual output: 0.35294117647058826	


1-5  -a- Enter sale: 10.00
	 Sale: 10.0
	 Tax: 0.7000000000000001
	 Total: 10.7

	      
     -b- Enter sale: 12.34
         Sale: 12.34
         Tax: 0.86       2 decimals is enough
         Total: 13.2      

	      
     -c- Enter sale:
         100.00
         Sale: 100.0
         Tax: 7.0
         Total: 107.0
	      
	
1-6 - only the following expressions evaluate to "true"
	   -a- 0                            -h- 1
	   -b- 4                            -i- 3
	   -c- false                        -j- true
	   -d- false                        -k- true
	   -e- false                        -l- false
	   -f- true                         -m- false
	   
	      
	 	
1-7     
import java.util.Scanner;

public class Average {

    public static void main (String[]args){
        Scanner kb = new Scanner(System.in);

        System.out.println("Enter test 1: ");
        double one = kb.nextDouble();

        System.out.println("Enter test 2: ");
        double two = kb.nextDouble();

        System.out.println("Enter test 3: ");
        double three = kb.nextDouble();

        System.out.println("Average = " + (one + two + three) / 3);
    }
}
	
1-8
    -a- 64.0
    -b- 3  (actually 3L, which is a long constant)
    -c- 2
    -d- 12.345
    -e- 4.57
	
1-9 intent error
    Although it compiles, the answer is wrong.  
    It is evaluating 4/100.0 instead of 100.0/4


1-10 correct intent error - corrections in ALL CAPS
     double sum, number;
     System.out.println("Enter sum: ");
     SUM = keyboard.nextInt();
     System.out.println("Enter number: );
     NUMBER = keyboard.nextInt();
     average = sum/number;
	
1-11 Explain the error
     keyboard (suspected to be a Scanner) is never instantiated
	
1-12 No 
     To correct, add parnethesis: double average = (x + y + z) / 3.0;