Questions and Answers
The isDigit, isLetter, and isLetterOrDigit methods are members of which class?
What method converts a character to uppercase?
toUpperCase
The startsWith, endsWith, and regionMatches methods are members of which class?
The indexOf and lastIndexOf methods are members of which class?
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The substring, getChars, and toCharArray methods are members of which class?
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What String class method performs the same operation as the + operator when used on strings?
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What is the name of the method that returns a string representation of a value for any primitive data type?
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If you do not pass an argument to the StringBuilder constructor, how many characters will it store?
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What is one method common to both the String and StringBuilder classes?
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To change the value of a specific character in a StringBuilder object, which method is used?
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To delete a specific character in a StringBuilder object, which method is used?
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What is the term for the character that separates tokens in a string?
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What String method breaks a string into tokens?
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What are the names of the variables that hold the minimum and maximum values for a particular data type?
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Character testing methods such as isLetter accept strings as arguments and test each character in the string.
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If the toUpperCase method's argument is already uppercase, it is returned as is with no changes.
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If the toLowerCase method's argument is already lowercase, it will be inadvertently converted to uppercase.
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The startsWith and endsWith methods are case-sensitive.
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There are two versions of the regionMatches method: one that is case-sensitive and one that can be case-insensitive.
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The indexOf and lastIndexOf methods can find characters, but cannot find substrings.
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The String class's replace method can replace individual characters, but cannot replace substrings.
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The StringBuilder class's replace method can replace individual characters, but cannot replace substrings.
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You can use the = operator to assign a string to a StringBuilder object.
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List some character class methods.
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What does isDigit(char ch) return?
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What does isLetter(char ch) return?
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What does isLowerCase(char ch) return?
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What does isUpperCase(char ch) return?
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What does char toLowerCase(char ch) return?
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What does char toUpperCase(char ch) return?
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List some String methods.
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What does indexOf(char ch) do?
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What does substring(int start) return?
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What does concat(String str) return?
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Study Notes
Character Class Methods
- The
isDigit
,isLetter
, andisLetterOrDigit
methods are part of the Character class. -
isDigit(char ch)
returns true ifch
is a digit (0-9). -
isLetter(char ch)
returns true ifch
is a letter. -
isLowerCase(char ch)
returns true ifch
is lowercase. -
isUpperCase(char ch)
returns true ifch
is uppercase. -
char toLowerCase(char ch)
returns the lowercase equivalent ofch
. -
char toUpperCase(char ch)
returns the uppercase equivalent ofch
.
String Class Methods
- The String class includes methods like
startsWith
,endsWith
,indexOf
, andlastIndexOf
. -
indexOf(char ch)
searches for the first occurrence ofch
in the string; returns the index or -1 if not found. -
substring(int start)
extracts a substring starting from the specified index to the end. -
concat(String str)
combines two strings and returns the resulting string. - The
replace
method can replace characters, and it has different overloads to replace substrings as well. -
valueOf()
returns a string representation of various primitive data types. -
split
method breaks a string into tokens based on a specified delimiter.
StringBuilder Class Methods
- The StringBuilder class allows mutable string operations.
- If no argument is passed to the StringBuilder constructor, it can store 16 characters by default.
- Common methods shared with String include
length()
. - To change a character, the
setCharAt(int index, char ch)
method is used. - The
deleteCharAt(int index)
method removes a character at a specified index. - The
replace(int start, int end, String str)
method can replace substrings, unlike the String class's replace method.
Object Manipulation and Behavior
- Using the
=
operator to assign a string to a StringBuilder object is not valid. - The
startsWith
andendsWith
methods are case-sensitive. - The String class methods
indexOf
andlastIndexOf
can locate substrings as well as characters. - Static final variables MIN_VALUE and MAX_VALUE are constants in numeric wrapper classes defining their limits.
- Character testing methods do not accept strings; they are designed for individual characters.
True/False Statements
-
False: Character testing methods like
isLetter
can operate on strings. - True: The toUpperCase method returns the original character if it's already uppercase.
- False: The toLowerCase method does not convert lowercase to uppercase.
-
True: Methods such as
startsWith
andendsWith
are case-sensitive. -
True:
regionMatches
has case-sensitive and case-insensitive versions. - True: The String class's replace method can replace characters but not substrings.
- False: The StringBuilder's replace method can replace substrings.
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Description
This quiz covers the important methods of the Character and String classes in Java. You'll learn how to determine character properties and manipulate strings effectively. Test your knowledge on methods such as isDigit
, toUpperCase
, indexOf
, and more!