Character and String Class Methods

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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 (C)</p> Signup and view all the answers

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

<p>String (D)</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 (B)</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 (B)</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 (A)</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 (B)</p> Signup and view all the answers

The startsWith and endsWith methods are case-sensitive.

<p>True (A)</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 (A)</p> Signup and view all the answers

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

<p>False (B)</p> Signup and view all the answers

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

<p>True (A)</p> Signup and view all the answers

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

<p>False (B)</p> Signup and view all the answers

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

<p>False (B)</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

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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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