Multiple Choice Questions on Java String Methods

📚 Quick Study Guide

• 🔤 String Immutability: Java Strings are immutable, meaning their values cannot be changed after they are created. Any modification results in a new String object.
• 📏 length(): Returns the number of characters in the string.
• 🔗 concat(String str): Concatenates the specified string to the end of the current string.
• ✂️ substring(int beginIndex, int endIndex): Returns a new string that is a substring of this string. The substring begins at the specified beginIndex and extends to the character at index endIndex - 1.
• 🔎 indexOf(String str): Returns the index within this string of the first occurrence of the specified substring.
• 🧽 trim(): Returns a string whose value is this string, with any leading and trailing whitespace removed.
• 🔄 replace(char oldChar, char newChar): Returns a new string resulting from replacing all occurrences of oldChar in this string with newChar.
• ✔️ equals(Object obj): Compares this string to the specified object. The result is true if and only if the argument is not null and is a String object that represents the same sequence of characters as this object.
• 🚫 equalsIgnoreCase(String anotherString): Compares this String to another String, ignoring case considerations.
• 🔡 toLowerCase(): Converts all of the characters in this String to lower case.
• 🔠 toUpperCase(): Converts all of the characters in this String to upper case.

Practice Quiz

1. Which of the following methods returns the length of a string?
   1. A. size()
   2. B. length()
   3. C. count()
   4. D. index()
2. What does the substring(int beginIndex, int endIndex) method do?
   1. A. Returns the character at the specified index.
   2. B. Returns a substring starting from beginIndex up to (but not including) endIndex.
   3. C. Returns a substring starting from beginIndex up to and including endIndex.
   4. D. Deletes a portion of the string.
3. Which method is used to compare two strings, ignoring case?
   1. A. equals()
   2. B. compare()
   3. C. equalsIgnoreCase()
   4. D. isEqual()
4. What is the purpose of the trim() method?
   1. A. To remove all spaces from a string.
   2. B. To remove leading and trailing whitespace from a string.
   3. C. To truncate a string to a specific length.
   4. D. To convert a string to lowercase.
5. Which method replaces all occurrences of a specified character in a string with another character?
   1. A. change()
   2. B. replace()
   3. C. switch()
   4. D. update()
6. What does the indexOf(String str) method return if the specified substring is not found?
   1. A. -1
   2. B. 0
   3. C. null
   4. D. false
7. What is the result of concatenating two strings in Java?
   1. A. The original strings are modified.
   2. B. A new string is created containing the combined text.
   3. C. An error is thrown.
   4. D. The first string is overwritten by the second string.