Java String Handling and Regular Expressions Flashcards

Which class from java.util.regex is used to perform match operations on input strings?

Answer: Matcher

A Matcher object is created from a Pattern and is used to perform matching operations on a character sequence.

What is the output of: new StringBuilder("Hello").reverse().toString();

Answer: olleH

StringBuilder.reverse() reverses the character sequence in place and returns the same StringBuilder, so toString() produces "olleH".

What does the regular expression "^[A-Z]" match?

Answer: A string that starts with an uppercase letter

The ^ anchor asserts the start of the string, so ^[A-Z] matches a string whose first character is an uppercase letter.

What is the difference between String.equals() and String.equalsIgnoreCase()?

Answer: equals() is case-sensitive; equalsIgnoreCase() ignores letter case differences

equals() performs a case-sensitive content comparison, while equalsIgnoreCase() treats uppercase and lowercase letters as equal.

What is the output of: String.format("%05d", 42);

Answer: "00042"

%05d formats the integer with a field width of 5, padding with leading zeros, producing "00042".

Which StringBuilder method appends a String to the end of the buffer?

Answer: append()

StringBuilder.append() adds the given value to the end of the character sequence in the buffer.

What does the regex quantifier {2,5} mean?

Answer: Between 2 and 5 occurrences (inclusive)

{2,5} is a bounded quantifier meaning the preceding element must occur at least 2 and at most 5 times.