CS 101-03 Quizzes

1. Date: Feb. 12, 2013
   Question: Which of the following words are NOT java identifiers? Explain.
   Answer:
   • age:
   • yorAge:
   • new: reserved word
   • old:
   • dynamic:
   • static: reserved word
   • total amount: contains the space character
   • student_count:
   • $total:
   • height^2: contains the ^ character
   • yaş:
   • kuru:
   • for: reserved word
   • mor:
   • why?: contains the ? character
   • why_not:
   • if: reserved word
   • mif:
   • me2:
   • 4you: starts with a digit

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2. Date: Feb. 19, 2013
   Question: What is the output of the following program segment?

   	int i = 7;
   	double d = 2.0;
   	boolean flag = true;
   	System.out.println("Value of i "+i);
   	System.out.println("Value of d/i is \rd/i");
   	System.out.println(flag+"\rg");
   	System.out.println("This is \n\tthe last line\b\b?");
   

   
   Answer:

   Value of i 7
   d/iue of d/i is
   grue
   This is
           the last li?e
   

   See the sample code.

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3. Date: Feb. 22, 2013
   Question: What is the output of the following program segment?

   	int a = 5;
   	System.out.println(++a);
   	System.out.println(a);
   	a = 7;
   	System.out.println(++a + a++);
   	System.out.println(a);
   

   
   Answer:

   6
   6
   16
   9
   

   See the sample code.

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4. Date: Feb. 26, 2013
   Question: Write a complete java program that reads ages of four persons from the keyboard and displays the average age of those people.
   Answer:

   /**
    * @(#)Q_03_4.java
    *
    * @author H. Altay Güvenir
    * @version 1.00 2013/2/26
    */
   import java.util.Scanner;
   
   public class Q_03_4 {
   	public static void main (String[] args) {
   		int totalAge = 0; // totalAge will store the total of the ages of the people
   		
   		Scanner keyboard = new Scanner(System.in); // Declare the keyboard
   
   		System.out.print("Enter the age of the first person: ");
   		totalAge += keyboard.nextInt(); // Read an age and add to the totalAge
   		
   		System.out.print("Enter the age of the second person: ");
   		totalAge += keyboard.nextInt(); // Read an age and add to the totalAge
   		
   		System.out.print("Enter the age of the third person: ");
   		totalAge += keyboard.nextInt(); // Read an age and add to the totalAge
   		
   		System.out.print("Enter the age of the fourth person: ");
   		totalAge += keyboard.nextInt(); // Read an age and add to the totalAge
   		// Now, totalAge contains the sum of the ages of the four people
   		
   		// Display the average age
   		System.out.println ("Their average is "+ totalAge/4.0);
   	} // main
   } // class Q_03_4 
   

   See the sample code.

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5. Date: Apr. 2, 2013
   Question: What is the output of the following program?

   public class Q_03_5 {
   
   	public static void main (String[] args) {
   		int count = 0;
   		int i = 4;
   		int j;
   
   		while (i > 0) {
   			j = i;
   			while (j-- > 0)
   				count ++;
   			i--;
   		} // outer while
   
   		// What is the output generated by the following statement?
   		System.out.println (count);
   	} // main
   } // class Q_01_5
   

   
   Answer:

   10
   

   See the sample code.

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6. Date: Apr. 5, 2013
   Question: Re-Write the following if-else statement using the switch statement.

   	if (harf == 'A')
   		System.out.println("Very Good");
   	else if (harf == 'B')
   		System.out.println("Good");
   	else if (harf == 'C')
   		System.out.println("OK");
   	else
   		System.out.println("Not Good");
   

   
   Answer:

   	switch (harf) {
   	case 'A' : 
   		System.out.println ("Very Good");
   		break;
   	case 'B' :
   		System.out.println ("Good");
   		break;
   	case 'C' :
   		System.out.println ("OK");
   		break;
   	default:
   		System.out.println ("Not Good");
   	} // switch
   

   See the sample code.

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7. Date: Apr. 9, 2013
   Question: Given the following do-while statement, write and equivalent for statement.

   	do {
   		System.out.print("Enter your age: ");
   		age = kb.nextInt();
   	} while (age<0 || age>120);
   

   
   Answer:

   	for (age = -1; age < 0 || age > 120; ) {
   		System.out.print("Enter your age: ");
   		age = kb.nextInt();
   	}	
   

   See the sample code.

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8. Date: Apr. 19, 2013
   Question: Write a method, called combination, that takes two int values, called m and n, and returns the value of C(m,n). Note, assume m > n.
   Answer:

   	private static int factorial (int n) {
   		int result = 1;
   		for (int i=2; i<=n; i++)
   			result *= i;
   		return result;
   	} // factorial
   		
   	public static int combination (int m, int n) {
   		return factorial(m) / factorial(n) / factorial(m-n);
   	} // combination	
   

   See the sample code.

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9. Date: Apr. 30, 2013
   Question: Write a method, called sum, that takes a double array, called d, as its formal parameter, and returns the sum of all values in the array, d.
   Answer:

   	public static double sum(double[] doubleArray) {
   		double sum = 0;
   		for (double d: doubleArray)
   			sum += d;
   		return sum;
   	} // sum
   

   See the sample code.

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