Chapter 2 Check Point Questions

2.12 If today is Tuesday, what will be the day in 100 days?

(2 + 100) % 7 = 4. So it is Thursday.

2.32 How would you write the following arithmetic expression? *Picture of the quadratic formula

(b + Math.pow(b * b â€" 4 * a * c, 0.5)) / (2 * a)

2.17 Suppose m and r are integers. Write a Java expression for mr 2 to obtain a floating-point result.

1.0 * m * (r * r)

2.24 Show the output of the following code: double a = 6.5; a += a + 1; System.out.println(a); a = 6; a /= 2; System.out.println(a);

14.0 3.0

2.11 Show the result of the following remainders. 56 % 6 78 % -4 -34 % 5 -34 % -5 5 % 1 1 % 5

2 2 -4 -4 0 1

2.31 Show the output of the following code: double amount = 5; System.out.println(amount / 2); System.out.println(5 / 2);

2.5 2

2.13 What is the result of 25 / 4? How would you rewrite the expression if you wished the result to be a floating-point number?

25 / 4 is 6. If you want the quotient to be a floating-point number, rewrite it as 25.0 / 4.0, 25.0 / 4, or 25 / 4.0.

2.20 Which of the following are the same as 52.534? 5.2534e+1, 0.52534e+2, 525.34e-1, 5.2534e+0

5.2534e+1, 0.52534e+2, 525.34e-1 are the same as 52.534.

2.21 Which of the following are correct literals? 5_2534e+1, _2534, 5_2, 5_

5_2534e+1, and 5_2, are correct.

2.26 Show the output of the following code: int a = 6; int b = a++; System.out.println(a); System.out.println(b); a = 6; b = ++a; System.out.println(a); System.out.println(b);

7 6 7 7

2.14 Show the result of the following code: System.out.println(2 * (5 / 2 + 5 / 2)); System.out.println(2 * 5 / 2 + 2 * 5 / 2); System.out.println(2 * (5 / 2)); System.out.println(2 * 5 / 2);

8 10 4 5

2.18 How many accurate digits are stored in a float or double type variable?

A float value has 7-8 number of accurate digits and a double value has 15-17 number of accurate digits.

2.37 What is a round-off error? Can integer operations cause round-off errors? Can floating-point operations cause round-off errors?

A round-off error, also called a rounding error, is the difference between the calculated approximation of a number and its exact mathematical value. Integer operations will not cause rounding error. Floating-point operations may cause rounding error.

2.19 Which of the following are correct literals for floating-point numbers? 12.3, 12.3e+2, 23.4e-2, â€"334.4, 20.5, 39F, 40D

All can be used as literals for floating-point numbers.

2.8 What are the naming conventions for class names, method names, constants, and variables? Which of the following items can be a constant, a method, a variable, or a class according to the Java naming conventions? MAX_VALUE, Test, read, readDouble

Class names: Capitalize the first letter in each name. Variables and method names: Lowercase the first word, capitalize the first letter in all subsequent words. Constants: Capitalize all letters. Constant: MAX_VALUE Method or variable: read , readDouble Class name: Test

2.33 Show the output with the input value 1.99.

Enter an amount in double, for example 11.56: 1.99 Your amount 1.99 consists of 1 dollars 3 quarters 2 dimes 0 nickels 4 pennies

2.10 Find the largest and smallest byte, short, int, long, float, and double. Which of these data types requires the least amount of memory?

For byte, from -128 to 127, inclusive. For short, from -32768 to 32767, inclusive. For int, from -2147483648 to 2147483647, inclusive. For long, from -9223372036854775808 to 9223372036854775807. For float, the smallest positive float is 1.40129846432481707e-45 and the largest float is 3.40282346638528860e+38. For double, the smallest positive double is 4.94065645841246544e-324 and the largest double is 1.79769313486231570e+308d.

2.1 Identify and fix the errors in the following code: 1 public class Test { 2 public void main(string[] args) { 3 double i = 50.0; 4 double k = i + 50.0; 5 double j = k + 1; 6 7 System.out.println("j is " + j + " and 8 k is " + k); 9 } 10 }

Line 2: Missing static for the main method. Line 2: string should be String. Lines 7-8: The string cannot be broken into two lines.

2.5 Identify and fix the errors in the following code: 1 public class Test { 2 public static void main(String[] args) { 3 int i = k + 2; 4 System.out.println(i); 5 } 6 }

Line 3: k is undefined.

2.16 Write a statement to display the result of 2 3.5 .

Math.pow(2, 3.5)

2.34 Can you declare a variable as int and later redeclare it as double?

No.

2.36 Will overflow cause a runtime error?

No.

2.6 Identify and fix the errors in the following code: 1 public class Test { 2 public static void main(String[] args) { 3 int i = j = k = 2; 4 System.out.println(i + " " + j + " " + k); 5 } 6 }

Note that the statement int i = j = k = 2 in line 3 only declares i. j and k are not declared. The following line would declare i, j, and k: int i, j, k; To fix the error, change line 3 to int j, k; int i = j = k = 2; or int i = 2; int j = 2; int k = 2; or int i = 2, j = 2, k = 2;

2.35 What is an integer overflow? Can floating-point operations cause overflow?

Numbers are stored with a limited numbers of digits. When a variable is assigned a value that is too large (in size) to be stored, it causes overflow. Overflow is for integer operations. Floating-point operations will not cause overflow.

2.30 If you change (int)(tax * 100) / 100.0 to (int)(tax * 100) / 100 in line 11 in Listing 2.8, what will be the output for the input purchase amount of 197.556?

The answer is 11 Here is the reason: tax = purchaseAmount * 0.06 = 197.556 * 0.06 = 11.85336 tax * 100 = 1185.336 (int)(tax * 100) = 1185 1185/ 100 = 11

2.28 What does an explicit casting from a double to an int do with the fractional part of the double value? Does casting change the variable being cast?

The fractional part is truncated. Casting does not change the variable being cast.

2.7 What are the benefits of using constants? Declare an int constant SIZE with value 20.

There are three benefits of using constants: (1) you don't have to repeatedly type the same value; (2) the value can be changed in a single location, if necessary; (3) the program is easy to read. final int SIZE = 20;

2.4 Which of the following identifiers are valid? Which are Java keywords? miles, Test, a++, --a, 4#R, $4, #44, apps class, public, int, x, y, radius

Valid identifiers: miles, Test, $4, apps, x, y, radius Invalid identifiers: a++, --a, 4#R, #44, class, public, int Keywords: class, public, int

2.15 Are the following statements correct? If so, show the output. System.out.println("25 / 4 is " + 25 / 4); System.out.println("25 / 4.0 is " + 25 / 4.0); System.out.println("3 * 2 / 4 is " + 3 * 2 / 4); System.out.println("3.0 * 2 / 4 is " + 3.0 * 2 / 4);

Yes, the statements are correct. The output is 25 / 4 is 6 25 / 4.0 is 6.25 3 * 2 / 4 is 1 3.0 * 2 / 4 is 1.5

2.27 Can different types of numeric values be used together in a computation?

Yes. Different types of numeric values can be used in the same computation through numeric conversions referred to as casting.

2.25 Which of these statements are true? a. Any expression can be used as a statement. b. The expression x++ can be used as a statement. c. The statement x = x + 5 is also an expression. d. The statement x = y = x = 0 is illegal.

b and c are true.

2.22 How would you write the following arithmetic expression in Java? a.

b. 5.5 × (r + 2.5) 2.5 + t (a) 4.0 / (3 * (r + 34)) â€" 9.0 / (a + b * c) + (3 + d * (2 + a) )/ (a + b * d) (b) 5.5 * Math.pow(r + 2.5, 2.5 + t)

2.9 Translate the following algorithm into Java code: Step 1: Declare a double variable named miles with initial value 100. Step 2: Declare a double constant named KILOMETERS_PER_MILE with value 1.609. Step 3: Declare a double variable named kilometers, multiply miles and KILOMETERS_PER_MILE, and assign the result to kilometers. Step 4: Display kilometers to the console. What is kilometers after Step 4?

double miles = 100; final double KILOMETERS_PER MILE = 1.609; double kilometers = KILOMETERS_PER MILE * miles; System.out.println(kilometers); The value of kilometers is 160.9.

2.2 How do you write a statement to let the user enter a double value from the keyboard? What happens if you entered 5a when executing the following code?

double radius = input.nextDouble(); Use Scanner input = new Scanner(System.in); double value = input.nextDouble(); A runtime error will occur if you entered 5a when executing the following code: double radius = input.nextDouble();

2.29 Show the output of the following code: float f = 12.5F; int i = (int)f; System.out.println("f is " + f); System.out.println("i is " + i);

f is 12.5 i is 12

2.3 Are there any performance differences between the following two import statements?

import java.util.Scanner; import java.util.*; No

2.23 How do you obtain the current second, minute, and hour?

long totalMills = System.currentTimeMillis() returns the milliseconds since Jan 1, 1970. long totalSeconds = totalMills / 1000 returns the total seconds. long totalMinutes = totalSeconds / 60 returns the total minutes. totalSeconds % 60 returns the current second. totalMinutes % 60 returns the current minute. totalMinutes / 60 % 24 returns the current hour.