All Flashcards
What does the following code output?
java
String s = "abc";
System.out.println(s.substring(1, 3));
bc
Identify the error in the following code:
java
String s = "hello";
for (int i = 0; i <= s.length(); i++) {
System.out.println(s.charAt(i));
}
IndexOutOfBoundsException: Loop should be i < s.length().
What does the following code output?
java
String s1 = "hello";
String s2 = new String("hello");
System.out.println(s1.equals(s2));
true
What does the following code output?
java
String s = "world";
String result = "";
for (int i = 0; i < s.length(); i++) {
result = result + s.charAt(i);
}
System.out.println(result);
world
Identify the error in the following code:
java
String s = "test";
System.out.println(s.substring(2, 1));
StringIndexOutOfBoundsException: endIndex cannot be less than beginIndex.
What does the following code output?
java
String s = "apple";
System.out.println(s.length());
5
What does the following code output?
java
String s = "OpenAI";
System.out.println(s.substring(4));
AI
Identify the error in the following code:
java
String s = null;
System.out.println(s.length());
NullPointerException: Cannot call length() on a null string.
What does the following code output?
java
String s1 = "hello";
String s2 = "Hello";
System.out.println(s1.equals(s2));
false
What does the following code output?
java
String s = "programming";
System.out.println(s.indexOf("gram"));
3
Difference between substring() and charAt()?
substring(): Returns a substring. charAt(): Returns a single character.
Difference between equals() and == for strings?
equals(): Compares content. ==: Compares references.
Difference between indexOf() and lastIndexOf()?
indexOf(): First occurrence. lastIndexOf(): Last occurrence.
Difference between toLowerCase() and toUpperCase()?
toLowerCase(): Converts to lowercase. toUpperCase(): Converts to uppercase.
Difference between replace() and replaceAll()?
replace(): Replaces first occurrence. replaceAll(): Replaces all occurrences (uses regex).
Difference between using a for loop and a while loop for string iteration?
for: Typically used when the number of iterations is known. while: Used when the number of iterations is unknown.
Difference between using StringBuilder and String for string manipulation?
String: Immutable, creates new objects. StringBuilder: Mutable, modifies the existing object.
Difference between using contains() and manually checking for a substring?
contains(): Built-in method, simpler. Manual: More control, potentially more efficient for specific cases.
Difference between using split() with a regular expression and a simple delimiter?
Regex: More flexible, handles complex patterns. Simple: Faster for basic delimiters.
Difference between using trim() and manually removing whitespace?
trim(): Removes leading and trailing whitespace. Manual: More control over which whitespace to remove.
What is a string?
A sequence of characters.
What is substring()?
A method that returns a portion of a string.
What does equals() do?
Compares two strings for content equality.
What is an index in a string?
The position of a character in the string, starting from 0.
Define 'string reversal'.
Creating a new string with characters in reverse order.
What is a 'sliding window'?
A technique to process substrings of a fixed size.
Define 'substring'.
A contiguous sequence of characters within a string.
What is string immutability?
The property that strings cannot be changed after creation.
What is the purpose of length()?
Returns the number of characters in a string.
What is string concatenation?
Joining two or more strings end-to-end.