SCJP Java String Handling and Regular Expressions 3

Question 1

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

Accepted Answer

Matcher

Answer

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

Question 2

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

Accepted Answer

olleH

Answer

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

Question 3

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

Accepted Answer

A string that starts with an uppercase letter

Answer

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

Question 4

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

Accepted Answer

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

Answer

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

Question 5

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

Accepted Answer

"00042"

Answer

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

SCJP - Sun Certified Java Programmer Practice Test