CSCI | Chapter 3 Check Point Questions
Rewrite the following conditional expressions using if-else statements. a. score = (x > 10) ? 3 * scale : 4 * scale; b. tax = (income > 10000) ? income * 0.2 : income * 0.17 + 1000; c. System.out.println((number % 3 == 0) ? i : j);
(a) if (x > 10) score = 3 * scale; else score = 4 * scale; (b) if (income > 10000) tax = income * 0.2; else tax = income * 0.17 + 1000; (c) if (number % 3 == 0) System.out.println(i); else System.out.println(j);
a. How do you generate a random integer i such that 0 <= i < 20 ? b. How do you generate a random integer i such that 10 <= i < 20 c. How do you generate a random integer i such that 10 <= i <= 50 d. Write an expression that returns 0 or 1 randomly.
(a) (int)(Math.random() * 20) (b) 10 + (int)(Math.random() * 10) (c) 10 + (int)(Math.random() * 41) (d) (int)(Math.random() * 2)
(a) Write a Boolean expression for |x - 5| < 4.5. (b) Write a Boolean expression for |x - 5| > 4.5.
(a) (x - 5) < 4.5 && (x - 5) > -4.5 (b) (x - 5) > 4.5 || (x - 5) < -4.5
(a) Write a Boolean expression that evaluates to true if a number stored in variable num is between 1 and 100. (b) Write a Boolean expression that evaluates to true if a number stored in variable num is between 1 and 100 or the number is negative.
(a) (x > 1) && (x < 100) (b) (num > 1) && (num < 100) || num < 0
Write conditional expression that returns -1 or 1 randomly.
(int)(Math.random() * 2) == 0 ? -1 : 1;
List six relational operators
<, <=, ==, !=, >, >=
Assuming that x is 1, show the result of the following Boolean expressions. (true) && (3 > 4) !(x > 0) && (x > 0) (x > 0) || (x < 0) (x != 0) || (x == 0) (x >= 0) || (x < 0) (x != 1) == !(x == 1)
(true) && (3 > 4) is false !(x > 0) && (x > 0) is false (x > 0) || (x < 0) is true (x != 0) || (x == 0) is true (x >= 0) || (x < 0) is true (x != 1) == !(x == 1) is true
Suppose, when you run the following program, you enter the input 2 3 6 from the console. What is the output? public class Test { public static void main(String[] args) { java.util.Scanner input = new java.util.Scanner(System.in); double x = input.nextDouble(); double y = input.nextDouble(); double z = input.nextDouble(); System.out.println("(x < y && y < z) is " + (x < y && y < z)); System.out.println("(x < y || y < z) is " + (x < y || y < z)); System.out.println("!(x < y) is " + !(x < y)); System.out.println("(x + y < z) is " + (x + y < z)); System.out.println("(x + y > z) is " + (x + y > z)); } }
(x < y && y < z) is true (x < y || y < z) is true !(x < y) is false (x + y < z) is true (x + y > z) is false
Which of the following is a possible output from invoking Math.random()? 323.4, 0.5, 34, 1.0, 0.0, 0.234
0.5, 0.0, 0.234
Are the following statements correct? Which one is better? (a) if (age < 16) System.out.println ("Cannot get a driver's license"); if (age >= 16) System.out.println ("Can get a driver's license"); (b) if (age < 16) System.out.println ("Cannot get a driver's license"); else System.out.println("Can get a driver's license");
Both are correct. (b) is better.
Evaluate the following expressions: 2 * 2 - 3 > 2 && 4 - 2 > 5 2 * 2 - 3 > 2 || 4 - 2 > 5
Both are false
Can the following conversions involving casting be allowed? Write a test program to verify it. boolean b = true; i = (int)b; int i = 1; boolean b = (boolean)i;
No. Boolean values cannot be cast to other types.
Assume that x and y are int type. Which of the following are legal Java expressions? x > y > 0 x = y && y x /= y x or y x and y (x != 0) || (x = 0)
x > y > 0 is incorrect x = y && y is incorrect x /= y is correct x or y is incorrect x and y is incorrect (x != 0) || (x = 0) is incorrect on x = 0
What is the output of the following code if number is 14, 15, or 30? (a) if (number % 2 == 0) System.out.println (number + " is even"); if (number % 5 == 0) System.out.println (number + " is multiple of 5"); (b) if (number % 2 == 0) System.out.println (number + " is even"); else if (number % 5 == 0) System.out.println (number + " is multiple of 5");
For (a) if number is 14, the output is 14 is even if number is 15, the output is 15 is multiple of 5 if number is 30, the output is 30 is even 30 is multiple of 5 For (b) if number is 14, the output is 14 is even If number is 15, the output is 15 is multiple of 5 if number is 30, the output is 30 is even
What is the output of the code in (a) and (b) if number is 30? What if number is 35? (a) if (number % 2 == 0) System.out.println(number + " is even."); System.out.println(number + " is odd."); (b) if (number % 2 == 0) System.out.println(number + " is even."); else System.out.println(number + " is odd.");
If number is 30, (a) displays 30 is even 30 is odd (b) displays 30 is even If number is 35, (a) displays 35 is odd (b) displays 35 is odd
What is the value of the expression x >= 50 && x <= 100 if x is 45, 67, or 101?
If x is 45, the expression is false. If x is 67, the expression is true. If x is 101, the expression is false.
What is wrong in the following code? if (score >= 60.0) System.out.println("D"); else if (score >= 70.0) System.out.println("C"); else if (score >= 80.0) System.out.println("B"); else if (score >= 90.0) System.out.println("A"); else System.out.println("F"); Consider score 90, what will be the grade?
It will be D
Suppose x = 2 and y = 3. Show the output, if any, of the following code. What is the output if x = 3 and y = 2? What is the output if x = 3 and y = 3? if (x > 2) if (y > 2) { int z = x + y; System.out.println("z is " + z); } else System.out.println("x is " + x);
No output if x = 2 and y = 3. Output is "x is 3" if x = 3 and y = 2. Output is "z is 6" if x = 3 and y = 3.
Suppose that, when you run the following program, you enter the input 2 3 6 from the console. What is the output? public class Test { public static void main(String[] args) { java.util.Scanner input = new java.util.Scanner(System.in); double x = input.nextDouble(); double y = input.nextDouble(); double z = input.nextDouble(); System.out.println((x < y && y < z) ? "sorted" : "not sorted"); } }
Sorted
What data types are required for a switch variable? If the keyword break is not used after a case is processed, what is the next statement to be executed? Can you convert a switch statement to an equivalent if statement, or vice versa? What are the advantages of using a switch statement?
Switch variables must be of char, byte, short, int, or String types. If a break statement is not used, the next case statement is performed. You can always convert a switch statement to an equivalent if statement, but not an if statement to a switch statement. The use of the switch statement can improve readability of the program in some cases. The compiled code for the switch statement is also more efficient than its corresponding if statement.
What is y after the following switch statement is executed? Rewrite the code using an if-else statement. x = 3; y = 3; switch (x + 3) { case 6: y = 1; default: y += 1; } x = 3; y = 3; if (x + 3 == 6) { y = 1; } y += 1;
y is 2
List the precedence order of the Boolean operators. Evaluate the following expressions: true || true && false true && true || false
The precedence order for boolean operators is !, ^, &&, and || true || true && false is true true && true || false is true
True or false? All the binary operators except = are left associative.
True
Are the following two expressions the same? (a) x % 2 == 0 && x % 3 == 0 (b) x % 6 == 0
Yes
Are the following two statements equivalent? (a) if (income <= 10000) tax = income * 0.1; else if (income <= 20000) tax = 1000 + (income - 10000) * 0.15; (b) if (income <= 10000) tax = income * 0.1; else if (income > 10000 && income <= 20000) tax = 1000 + (income - 10000) * 0.15;
Yes
Is x > 0 && x < 10 the same as x > 0 && x < 10? Is x > 0 || x < 10 the same as x > 0 || x < 10? Is (x > 0 || x < 10) && y < 0 the same as (x > 0 || (x < 10 && y < 0))?
Yes. Yes. Yes.
Which of the following statements are equivalent? Which ones are correctly indented? (a) if (i > 0) if (j > 0) x = 0; else if (k > 0) y = 0; else z = 0; (b) if (i > 0) { if (j > 0) x = 0; else if (k > 0) y = 0; } else z = 0; (c) if (i > 0) if (j > 0) x = 0; else if (k > 0) y = 0; else z = 0; (d) if (i > 0) if (j > 0) x = 0; else if (k > 0) y = 0; else z = 0;
a, c, and d are the same. (B) and (C) are correctly indented.
Write a Boolean expression that evaluates to true if age is greater than 13 and less than 18.
age > 13 && age < 18
Write an if statement that increases pay by 3% if score is greater than 90.
if (score > 90) pay *= 1.03;
Write an if statement that increases pay by 3% if score is greater than 90, otherwise increases pay by 1%.
if (score > 90) pay *= 1.03; else pay *= 1.01;
Write an if statement that assigns 1 to x if y is greater than 0.
if (y > 0) x = 1;
Rewrite the following statement using a Boolean expression: if (count % 10 == 0) newLine = true; else newLine = false;
newLine = (count % 10 == 0);
Write a switch statement that displays Sunday, Monday, Tuesday, Wednesday, Thursday, Friday, Saturday, if day is 0, 1, 2, 3, 4, 5, 6, accordingly.
switch (day) { case 0: System.out.println("Sunday"); break; case 1: System.out.println("Monday"); break; case 2: System.out.println("Tuesday"); break; case 3: System.out.println("Wednesday"); break; case 4: System.out.println("Thurday"); break; case 5: System.out.println("Friday"); break; case 6: System.out.println("Saturday"); break; }
Rewrite the following if statements using the conditional operator. if (ages >= 16) ticketPrice = 20; else ticketPrice = 10;
ticketPrice = (ages >= 16) ? 20 : 10;
Assuming that x is 1, show the result of the following Boolean expressions: x > 0 x < 0 x != 0 x >= 0 x != 1
true false true true false
Write a Boolean expression that evaluates to true if weight is greater than 50 pounds and height is greater than 60 inches.
weight > 50 && height > 60.
Write a Boolean expression that evaluates to true if either weight is greater than 50 pounds or height is greater than 60 inches, but not both.
weight > 50 ^ height > 60.
Write a Boolean expression that evaluates to true if weight is greater than 50 pounds or height is greater than 60 inches.
weight > 50 || height > 60.
