Chapter 4 Check Point Questions
Section 4.2
▼4.2.1
Evaluate the following method calls:
(a) Math.sqrt(4) (b) Math.sin(2 * Math.PI) (c) Math.cos(2 * Math.PI) (d) Math.pow(2, 2) (e) Math.log(Math.E) (f) Math.exp(1) (g) Math.max(2, Math.min(3, 4)) (h) Math.rint(-2.5) (i) Math.ceil(-2.5) (j) Math.floor(-2.5) (k) Math.round(-2.5f) (l) Math.round(-2.5) (m) Math.rint(2.5) (n) Math.ceil(2.5) (o) Math.floor(2.5) (p) Math.round(2.5f) (q) Math.round(2.5) (r) Math.round(Math.abs(-2.5))
▼4.2.2
True or false? The argument for trigonometric methods is an angle in radians.
▼4.2.3
Write a statement that converts 47 degrees to radians and assigns the result to a variable.
▼4.2.4
Write a statement that converts π / 7 to an angle in degrees and assigns the result to a variable.
▼4.2.5
Write an expression that obtains a random integer between 34 and 55. Write an expression that obtains a random integer between 0 and 999. Write an expression that obtains a random number between 5.5 and 55.5.
▼4.2.6
Why does the Math class not need to be imported?
▼4.2.7
What is Math.log(Math.exp(5.5))? What is Math.exp(Math.log(5.5))? What is Math.asin(Math.sin(Math.PI / 6))? What is Math.sin(Math.asin(Math.PI / 6))?
Section 4.3
▼4.3.1
Use print statements to find out the ASCII code for '1', 'A', 'B', 'a', and 'b'. Use print statements to find out the character for the decimal codes 40, 59, 79, 85, and 90. Use print statements to find out the character for the hexadecimal code 40, 5A, 71, 72, and 7A.
▼4.3.2
Which of the following are correct literals for characters?
'1', '\u345dE', '\u3fFa', '\b', '\t'
▼4.3.3
How do you display the characters \ and "?
▼4.3.4
Evaluate the following:
int i = '1'; int j = '1' + '2' * ('4' - '3') + 'b' / 'a'; int k = 'a'; char c = 90;
▼4.3.5
Can the following conversions involving casting be allowed? If so, find the converted result.
char c = 'A'; int i = (int)c; float f = 1000.34f; int i = (int)f; double d = 1000.34; int i = (int)d; int i = 97; char c = (char)i;
▼4.3.6
Show the output of the following program:
public class Test { public static void main(String[] args) { char x = 'a'; char y = 'c'; System.out.println(++x); System.out.println(y++); System.out.println(x - y); } }
▼4.3.7
Write the code that generates a random lowercase letter.
▼4.3.8
Show the output of the following statements:
System.out.println('a' < 'b'); System.out.println('a' <= 'A'); System.out.println('a' > 'b'); System.out.println('a' >= 'A'); System.out.println('a' == 'a'); System.out.println('a' != 'b');
Section 4.4
▼4.4.1
Suppose that s1, s2, and s3 are three strings, given as follows:
String s1 = "Welcome to Java"; String s2 = "Programming is fun"; String s3 = "Welcome to Java";What are the results of the following expressions?
a. s1 == s2 b. s2 == s3 c. s1.equals(s2) d. s1.equals(s3) e. s1.compareTo(s2) f. s2.compareTo(s3) g. s2.compareTo(s2) h. s1.charAt(0) i. s1.indexOf('j') j. s1.indexOf("to") k. s1.lastIndexOf('a') l. s1.lastIndexOf("o", 15) m. s1.length() n. s1.substring(5) o. s1.substring(5, 11) p. s1.startsWith("Wel") q. s1.endsWith("Java") r. s1.toLowerCase() s. s1.toUpperCase() t. s1.concat(s2) u. s1.contains(s2) v. "\t Wel \t".trim()
▼4.4.2
Suppose that s1 and s2 are two strings. Which of the following statements or expressions are incorrect?
String s = "Welcome to Java"; String s3 = s1 + s2; String s3 = s1 - s2; s1 == s2; s1 >= s2; s1.compareTo(s2); int i = s1.length(); char c = s1(0); char c = s1.charAt(s1.length());
▼4.4.3
Show the output of the following statements (write a program to verify your results):
System.out.println("1" + 1); System.out.println('1' + 1); System.out.println("1" + 1 + 1); System.out.println("1" + (1 + 1)); System.out.println('1' + 1 + 1);
▼4.4.4
Evaluate the following expressions (write a program to verify your results):
1 + "Welcome " + 1 + 1 1 + "Welcome " + (1 + 1) 1 + "Welcome " + ('\u0001' + 1) 1 + "Welcome " + 'a' + 1
▼4.4.5
Let s1 be " Welcome " and s2 be " welcome ". Write the code for the following statements:
a. Check whether s1 is equal to s2 and assign the result to a Boolean variable isEqual.
b. Check whether s1 is equal to s2, ignoring case, and assign the result to a Boolean variable isEqual.
c. Compare s1 with s2 and assign the result to an int variable x.
d. Compare s1 with s2, ignoring case, and assign the result to an int variable x.
e. Check whether s1 has the prefix AAA and assign the result to a Boolean variable b.
f. Check whether s1 has the suffix AAA and assign the result to a Boolean variable b.
g. Assign the length of s1 to an int variable x.
h. Assign the first character of s1 to a char variable x.
i. Create a new string s3 that combines s1 with s2.
j. Create a substring of s1 starting from index 1.
k. Create a substring of s1 from index 1 to index 4.
l. Create a new string s3 that converts s1 to lowercase.
m. Create a new string s3 that converts s1 to uppercase.
n. Create a new string s3 that trims whitespaces on both ends of s1.
o. Assign the index of the first occurrence of the character e in s1 to an int variable x.
p. Assign the index of the last occurrence of the string abc in s1 to an int variable x.
a. Check whether s1 is equal to s2 and assign the result to a Boolean variable isEqual.
b. Check whether s1 is equal to s2, ignoring case, and assign the result to a Boolean variable isEqual.
c. Compare s1 with s2 and assign the result to an int variable x.
d. Compare s1 with s2, ignoring case, and assign the result to an int variable x.
e. Check whether s1 has the prefix AAA and assign the result to a Boolean variable b.
f. Check whether s1 has the suffix AAA and assign the result to a Boolean variable b.
g. Assign the length of s1 to an int variable x.
h. Assign the first character of s1 to a char variable x.
i. Create a new string s3 that combines s1 with s2.
j. Create a substring of s1 starting from index 1.
k. Create a substring of s1 from index 1 to index 4.
l. Create a new string s3 that converts s1 to lowercase.
m. Create a new string s3 that converts s1 to uppercase.
n. Create a new string s3 that trims whitespaces on both ends of s1.
o. Assign the index of the first occurrence of the character e in s1 to an int variable x.
p. Assign the index of the last occurrence of the string abc in s1 to an int variable x.
▼4.4.6
Write one statement to return the number of digits in an integer i.
▼4.4.7
Write one statement to return the number of digits in a double value d.
▼4.4.8
What is wrong in the following code?
import java.util.Scanner; public class Test { public static void main(String[] args) { Scanner input = new Scanner(System.in); System.out.print("Enter an integer: "); int value = input.nextInt(); System.out.println("The value is " + value); System.out.print("Enter a line: "); String line = input.nextLine(); System.out.println("The line is " + line); } }
Section 4.5
▼4.5.1
If you run Listing 4.3 GuessBirthday.java with input 1 for Set1, Set3, and Set4 and 0 for Set2 and Set5, what will be the birthday?
▼4.5.2
If you enter a lowercase letter such as b, the program in Listing 4.4 displays B
is 11. Revise the code so to display b is 11.
▼4.5.3
What would be wrong if lines 6-7 in Listing 4.5 is replaced by the following code?
String lottery = "" + (int)(Math.random() * 100);
String lottery = "" + (int)(Math.random() * 100);
Section 4.6
▼4.6.1
What are the format specifiers for outputting a Boolean value, a character, a decimal integer, a floating-point number, and a string?
▼4.6.2
What is wrong in the following statements?
(a) System.out.printf("%5d %d\n", 1, 2, 3); (b) System.out.printf("%5d %f\n", 1); (c) System.out.printf("%5d %f\n", 1, 2); (d) System.out.printf("%.2f\n%0.3f\n", 1.23456, 2.34); (e) System.out.printf("%08s\n", "Java");
▼4.6.3
Show the output of the following statements.
(a) System.out.printf("amount is %f %e\n", 32.32, 32.32); (b) System.out.printf("amount is %5.2f%% %5.4e\n", 32.327, 32.32); (c) System.out.printf("%6b\n", (1 > 2)); (d) System.out.printf("%6s\n", "Java"); (e) System.out.printf("%-6b%s\n", (1 > 2), "Java"); (f) System.out.printf("%6b%-8s\n", (1 > 2), "Java"); (g) System.out.printf("%,5d %,6.1f\n", 312342, 315562.932); (h) System.out.printf("%05d %06.1f\n", 32, 32.32);