Chapter 4 Mathematical Functions, Characters, and Strings

Section 4.2 Common Mathematical Functions 
Section 4.2.1 Trigonometric Methdos
1.	To obtain the sine of 35 degrees, use _______.
a.	Math.sin(35)
b.	Math.sin(Math.toRadians(35))
c.	Math.sin(Math.toDegrees(35))
d.	Math.sin(Math.toRadian(35))
e.      Math.sin(Math.toDegree(35))
Key:b Note the trig methods use the radians for angles.

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2.	To obtain the arc sine of 0.5, use _______.
a.	Math.asin(0.5)
b.	Math.asin(Math.toDegrees(0.5))
c.	Math.sin(Math.toRadians(0.5))
d.      Math.sin(0.5)
Key:a Note the trig methods use the radians for angles.

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3.	Math.asin(0.5) returns _______.
a.	30
b.	Math.toRadians(30)
c.	Math.PI / 4
d.      Math.PI / 2
Key:b Noteh that Math.asin returns an angle in radians.

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4.	Math.sin(Math.PI) returns _______.
a.	0.0
b.	1.0
c.	0.5
d.      0.4
Key:a  Note that Math.PI is 180 degrees.

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5.	Math.cos(Math.PI) returns _______.
a.	0.0
b.	1.0
c.	-1.0
d.      0.5
Key:c Note that Math.PI is 180 degrees.

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Section 4.2.3 The Rounding Methods
5.	What is Math.round(3.6)?
a.	3.0
b.	3
c.	4
d.	4.0
Key:c Note that round returns an int value

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6.	What is Math.rint(3.6)?
a.	3.0
b.	3
c.	4.0
d.	5.0
Key:c Note that rint returns a double value

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7.	What is Math.rint(3.5)?
a.	3.0
b.	3
c.	4
d.	4.0
e.	5.0
Key:d rint returns the nearest even integer as a double since 3.5 is equally close to 3.0 and 4.0.

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8.	What is Math.ceil(3.6)?
a.	3.0
b.	3
c.	4.0
d.	5.0
Key:c  Note that ceil returns a double value

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9.	What is Math.floor(3.6)?
a.	3.0
b.	3
c.	4
d.	5.0
Key:a Note that floor returns a double value

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Section 4.3 Character Data Type and Operations
Section 4.3.1 Unicode and ASCII Code
10.	Which of the following is the correct expression of character 4?
a.	4
b.	"4"
c.	'\0004'
d.  	'4'
Key:d You have to write '4'.

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11.	A Java character is stored in __________.
a.	one byte
b.	two bytes
c.	three bytes
d.	four bytes
Key:b Java characters use Unicode encoding.

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12.	The Unicode of 'a' is 97. What is the Unicode for 'c'?
a.	96
b.	97
c.	98
d.	99
Key:d The Unicode for letters and numbers are allocated in a natural order. So b is after a and c is after b, and so on.

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Section 4.3.2 Escape Sequences for Special Characters
13.	Which of the following statement prints smith\exam1\test.txt?
a.	System.out.println("smith\exam1\test.txt");
b.	System.out.println("smith\\exam1\\test.txt");
c.	System.out.println("smith\"exam1\"test.txt");
d.	System.out.println("smith"\exam1"\test.txt");
Key:b  To represent the \ character, use \\, because it is an escape character.

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Section 4.3.3 Casting between char and Numeric Types
14.	Suppose x is a char variable with a value 'b'. What is the output of the statement System.out.println(++x)?
a.	a
b.	b
c.	c
d.	d
Key:c  The ++ and -- operators can be applied to a char variable. ++x is preincrement. x is 'b' before ++x. After ++x, x becomes c.

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15.	Suppose i is an int type variable. Which of the following statements display the character whose Unicode is stored in variable i?
a.	System.out.println(i);
b.	System.out.println((char)i);
c.	System.out.println((int)i);
d.	System.out.println(i + " ");
Key:b (char)i casts a number into a character.

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16.	Will System.out.println((char)4) display 4?
a.	Yes
b.	No
Key:b The character whose Unicode is \u0004 is to be displayed, not number 4.

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17.	What is the output of System.out.println('z' - 'a')?
a.	25
b.	26
c.	a
d.	z
Key:a  The Unicode offset between z and a is 25. 

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18.	An int variable can hold __________.
a.	'x'
b.	120
c.	120.0
d.	"x"
e.      "120"
Key:ab Choice (A) is also correct, because a character can be implicitly cast into an int variable. The Unicode value of character is assignment to the int variable. In this case, the code is 120 (see Appendix B).

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19.	Which of the following assignment statements is correct?
a.	char c = 'd';
b.	char c = 100;
c.	char c =  "d";
d.	char c = "100";
Key:ab Choice (B) is also correct, because an int value can be implicitly cast into a char variable. The Unicode of the character is the int value. In this case, the character is d (see Appendix B).

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20.	'3' - '2' + 'm' / 'n' is ______.
a.	0
b.	1
c.	2
d.	3
Key:b  When an operand is a character in an arithmetic expression, the character is casted to an int value.

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Section 4.3.4 Comparing and Testing Characters
21. To check whether a char variable ch is an uppercase letter, you write ___________.
a.	(ch >= 'A' && ch >= 'Z')
b.	(ch >= 'A' && ch <= 'Z')
c.	(ch >= 'A' || ch <= 'Z')
d.	('A' <= ch <= 'Z')
Key:b  A is wrong because ch >= 'Z'. C is wrong because of using ||. D is wrong because of incorrect syntax. The correct answer is B.

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22.	Which of the following is not a correct method in the Character class?
a. isLetterOrDigit(char)
b. isLetter(char)
c. isDigit()
d. toLowerCase(char)
e. toUpperCase()
Key:ce isDigit() should be isDigit(char) and toUpperCase() should be toUpperCase(char)

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23. Suppose Character x = new Character('a'), __________________ returns true.
a.	x.equals(new Character('a'))
b.	x.compareToIgnoreCase('A')
c.	x.equalsIgnoreCase('A')
d.      x.equals('a')
e.      x.equals("a")
Key:ad  (B) and (C) are wrong because no methods compareToIgnoreCase and equalsIgnoreCase are in the Character class. (E) is wrong because a character is not a string.

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Section 4.4 The String Type
Section 4.4.2 Gettiing Characters from a String
24. Suppose s is a string with the value "java". What will be assigned to x if you execute the following code?

char x = s.charAt(4);
a. 'a'
b. 'v'
c. Nothing will be assigned to x, because the execution causes the runtime error StringIndexOutofBoundsException.
Key:c The string index starts from 0 and the last index is s.length() - 1. s.charAt(4) is out of bounds.

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Section 4.4.3 Concatenating Strings
25.	The expression "Java " + 1 + 2 + 3 evaluates to ________.
a. Java123
b. Java6
c. Java 123
d. java 123
e. Illegal expression
key:c The + operator is evaluated from left to right. When a string adds with a number, the number is converted into a string. The correct answer is C.

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26.	Note that the Unicode for character A is 65. The expression "A" + 1 evaluates to ________.
a. 66
b. B
c. A1
d. Illegal expression
key:c When a string adds with a number, the number is converted into a string. The correct answer is C.

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27.	Note that the Unicode for character A is 65. The expression 'A' + 1 evaluates to ________.
a. 66
b. B
c. A1
d. Illegal expression
key: a  When a character adds with a number, the character is converted into a int. The correct answer is A.

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Section 4.4.4 Converting Strings
28.	Which of the following is the correct statement to return JAVA?
a. toUpperCase("Java")
b. "Java".toUpperCase("Java")
c. "Java".toUpperCase()
d. String.toUpperCase("Java")
Key:c The correct method is toUpperCase(). So C is correct.

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Section 4.4.7 Comparing Strings
29.	Suppose s1 and s2 are two strings. Which of the following statements or expressions is incorrect?
a.	String s3 = s1 - s2;
b.	boolean b = s1.compareTo(s2);
c.	char c = s1[0];
d.	char c = s1.charAt(s1.length());
Key:abcd A is wrong because the - operator cannot be used for strings. B is wrong because the compareTo method returns an int, not a boolean. C is wrong because the [] cannot be used for accessing string elements. D is wrong because of index out of bounds.

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30.	Suppose s1 and s2 are two strings. What is the result of the following code?

    s1.equals(s2) == s2.equals(s1)
a.	true
b.	false
Key:a s1.equals(s2) and s2.equals(s1) are the same.

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31.	"abc".compareTo("aba") returns ___________.
a.	1
b.	2
c.	-1
d.	-2
e.      0
Key:b The first two characters in the two strings are the same. The different between the last two characters is 2. The correct answer is B.

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32.	"AbA".compareToIgnoreCase("abC") returns ___________.
a.	1
b.	2
c.	-1
d.	-2
e.      0
Key:d Ignoring case, you compare aba with abc. The first two characters in the two strings are the same. The different between the last two characters is -2. The correct answer is D.

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33.	____________________ returns true.
a.	"peter".compareToIgnoreCase("Peter")
b.	"peter".compareToIgnoreCase("peter")
c.	"peter".equalsIgnoreCase("Peter")
d.	"peter".equalsIgnoreCase("peter")
e.      "peter".equals("peter")
Key:cde The compareToIgnoreCase return an int. So, A and B are wrong. Ignoring case, C, D, and E all return true.

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Section 4.4.8 Obtaining Substrings
34.	What is the return value of "SELECT".substring(0, 5)?
a.	"SELECT"
b.	"SELEC"
c.	"SELE"
d.   	"ELECT"
Key:b Note that the sustring is from index 0 to 4, which is 5 - 1. The correct answer is B.

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35.	What is the return value of "SELECT".substring(4, 4)?
a.	an empty string
b.	C
c.	T
d.   	E
Key:a If beginIndex is endIndex, substring(beginIndex, endIndex) returns an empty string with length 0. It would be a runtime error, if beginIndex > endIndex.

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Section 4.4.9 Finding a Character or a Substring in a String
36.	To check if a string s contains the prefix "Java", you may write 

a. if (s.startsWith("Java")) ...
b. if (s.indexOf("Java") == 0) ...
c. if (s.substring(0, 4).equals("Java")) ...
d. if (s.charAt(0) == 'J' && s.charAt(1) == 'a' && s.charAt(2) == 'v' && s.charAt(3) == 'a') ...
Key:abcd They are all correct.

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37.	To check if a string s contains the suffix "Java", you may write 
a. if (s.endsWith("Java")) ...
b. if (s.lastIndexOf("Java") >= 0) ...
c. if (s.substring(s.length() - 4).equals("Java")) ...
d. if (s.substring(s.length() - 5).equals("Java")) ...
e. if (s.charAt(s.length() - 4) == 'J' && s.charAt(s.length() - 3) == 'a' && s.charAt(s.length() - 2) == 'v' && s.charAt(s.length() - 1) == 'a') ...
Key:ace s.lastIndexOf("Java") >= 0 does not indicate that Java is the suffix of the string.

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Section 4.4.10 Conversions between Strings and Numbers
38. The __________ method parses a string s to an int value.
a.	integer.parseInt(s);
b.	Integer.parseInt(s);
c.	integer.parseInteger(s);
d.	Integer.parseInteger(s);
Key:b The parseInt method is defined in the Integer class. B is correct.

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39. The __________ method parses a string s to a double value.
a.	double.parseDouble(s);
b.	Double.parsedouble(s);
c.	double.parse(s);
d.	Double.parseDouble(s);
Key:d The parseDouble method is defined in the Double class. D is correct.

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Section 4.6 Formatting Console Output
40. Which of the following are valid specifiers for the printf statement?
a.	%4c 
b.	%10b
c.	%6d
d.	%8.2d
e.      %10.2e
Key:abce All correct.

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41. The statement System.out.printf("%3.1f", 1234.56) outputs ___________.
a.	123.4 
b.	123.5
c.	1234.5
d.	1234.56
e.      1234.6
Key:e .1 specifies one digit after the decimal point. The rest is rounded up. So 1234.56 is displayed 1234.6.

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42. The statement System.out.printf("%3.1e", 1234.56) outputs ___________.
a.	0.1e+04 
b.	0.123456e+04
c.	0.123e+04
d.	1.2e+03
e.      1.23+03
Key:d %3.1e specifies a scientific notation with one digit after the decimal point. So, the correct answer is D.

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43. The statement System.out.printf("%5d", 123456) outputs ___________.
a.	12345 
b.	23456
c.	123456
d.	12345.6
Key:c %5d specifies an integer with width 5. The width is automatically expanded if the number is larger than the specified width. So, the correct answer is C.

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44. The statement System.out.printf("%10s", 123456) outputs ___________. (Note: * represents a space)
a.	123456**** 
b.	23456*****
c.	12345*****
d.	****123456
Key:d %10s specifies to display a string with width 10. By default, it is right justified. So, the correct answer is D.

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45. Analyze the following code:

int i = 3434; double d = 3434;
System.out.printf("%5.1f %5.1f", i, d);

a. The code compiles and runs fine to display 3434.0 3434.0.
b. The code compiles and runs fine to display 3434 3434.0.
c. i is an integer, but the format specifier %5.1f specifies a format for double value. The code has an error.
Key:c i is an integer, but the format specifier %5.1f specifies a format for double value. Type does not match. So, the correct answer is C.