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Character and String Class Methods
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Character and String Class Methods

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@SafePythagoras

Questions and Answers

The isDigit, isLetter, and isLetterOrDigit methods are members of which class?

  • StringBuilder
  • String
  • Math
  • Character (correct)

    • What method converts a character to uppercase?

    toUpperCase

    The startsWith, endsWith, and regionMatches methods are members of which class?

  • StringBuilder
  • ArrayList
  • Character
  • String (correct)

    • The indexOf and lastIndexOf methods are members of which class?

    <p>String</p> Signup and view all the answers

    The substring, getChars, and toCharArray methods are members of which class?

    <p>String</p> Signup and view all the answers

    What String class method performs the same operation as the + operator when used on strings?

    <p>concat</p> Signup and view all the answers

    What is the name of the method that returns a string representation of a value for any primitive data type?

    <p>valueOf</p> Signup and view all the answers

    If you do not pass an argument to the StringBuilder constructor, how many characters will it store?

    <p>16</p> Signup and view all the answers

    What is one method common to both the String and StringBuilder classes?

    <p>length</p> Signup and view all the answers

    To change the value of a specific character in a StringBuilder object, which method is used?

    <p>setCharAt</p> Signup and view all the answers

    To delete a specific character in a StringBuilder object, which method is used?

    <p>deleteCharAt</p> Signup and view all the answers

    What is the term for the character that separates tokens in a string?

    <p>delimiter</p> Signup and view all the answers

    What String method breaks a string into tokens?

    <p>split</p> Signup and view all the answers

    What are the names of the variables that hold the minimum and maximum values for a particular data type?

    <p>MIN_VALUE and MAX_VALUE</p> Signup and view all the answers

    Character testing methods such as isLetter accept strings as arguments and test each character in the string.

    <p>False</p> Signup and view all the answers

    If the toUpperCase method's argument is already uppercase, it is returned as is with no changes.

    <p>True</p> Signup and view all the answers

    If the toLowerCase method's argument is already lowercase, it will be inadvertently converted to uppercase.

    <p>False</p> Signup and view all the answers

    The startsWith and endsWith methods are case-sensitive.

    <p>True</p> Signup and view all the answers

    There are two versions of the regionMatches method: one that is case-sensitive and one that can be case-insensitive.

    <p>True</p> Signup and view all the answers

    The indexOf and lastIndexOf methods can find characters, but cannot find substrings.

    <p>False</p> Signup and view all the answers

    The String class's replace method can replace individual characters, but cannot replace substrings.

    <p>True</p> Signup and view all the answers

    The StringBuilder class's replace method can replace individual characters, but cannot replace substrings.

    <p>False</p> Signup and view all the answers

    You can use the = operator to assign a string to a StringBuilder object.

    <p>False</p> Signup and view all the answers

    List some character class methods.

    <p>isDigit(char ch), isLetter(char ch), isLowerCase(char ch), isUpperCase(char ch), char toLowerCase(char ch), char toUpperCase(char ch)</p> Signup and view all the answers

    What does isDigit(char ch) return?

    <p>true if the argument passed into ch is a digit from 0-9</p> Signup and view all the answers

    What does isLetter(char ch) return?

    <p>true if the argument passed into ch is a letter</p> Signup and view all the answers

    What does isLowerCase(char ch) return?

    <p>true if argument is lowercase</p> Signup and view all the answers

    What does isUpperCase(char ch) return?

    <p>true if argument is uppercase</p> Signup and view all the answers

    What does char toLowerCase(char ch) return?

    <p>returns lowercase equivalent of argument passed to ch</p> Signup and view all the answers

    What does char toUpperCase(char ch) return?

    <p>returns uppercase equivalent of argument passed to ch</p> Signup and view all the answers

    List some String methods.

    <p>indexOf(char ch), substring(int start), concat(String str), String replace(char oldChar, char newChar), String valueOf()</p> Signup and view all the answers

    What does indexOf(char ch) do?

    <p>searches the calling string object for the character passed into ch. If found, returns its first occurrence's position; otherwise, returns -1</p> Signup and view all the answers

    What does substring(int start) return?

    <p>returns a copy of the substring that begins at start and goes to the end of the calling object's string</p> Signup and view all the answers

    What does concat(String str) return?

    <p>returns a copy of the calling string object with the contents of str concatenated to it</p> Signup and view all the answers

    Study Notes

    Character Class Methods

    • The isDigit, isLetter, and isLetterOrDigit methods are part of the Character class.
    • isDigit(char ch) returns true if ch is a digit (0-9).
    • isLetter(char ch) returns true if ch is a letter.
    • isLowerCase(char ch) returns true if ch is lowercase.
    • isUpperCase(char ch) returns true if ch is uppercase.
    • char toLowerCase(char ch) returns the lowercase equivalent of ch.
    • char toUpperCase(char ch) returns the uppercase equivalent of ch.

    String Class Methods

    • The String class includes methods like startsWith, endsWith, indexOf, and lastIndexOf.
    • indexOf(char ch) searches for the first occurrence of ch 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 and endsWith methods are case-sensitive.
    • The String class methods indexOf and lastIndexOf 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 and endsWith 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!

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