Strings

Question 1

True or False

Strings are mutable

Answer 1

False

Question 2

What class can be used to obtain a mutable representation of a String?

Answer 2

StringBuilder or StringBuffer

Question 3

True or False

String implements Comparable<String>

Answer 3

True

Question 4

What is the difference between StringBuilder and StringBuffer?

Answer 4

StringBuffer is thread safe but StringBuilder is not

Question 5

Valid or Invalid?

String str = "abc";
System.out.println(str[0]);

Answer 5

Invalid. str would need to be converted to a char[] by calling toCharArray()

Question 6

Are strings iterable?

Answer 6

No. However, the toCharArray() method can be used to generate a newly created char array that can be iterated

Question 7

Code an example of sorting a String using Arrays

Answer 7

        String str = "dcba";
        char[] arr = str.toCharArray();
        Arrays.sort(arr);
        String copy = String.valueOf(arr);

Question 8

True or False

StringBuilder overrides equals() like String

Answer 8

False

Question 9

Code an example of sorting a String using Stream

Answer 9

StringBuilder builder = s.chars()
           .mapToObj(e -> (char) e)
           .sorted()
           .collect(StringBuilder::new, StringBuilder::append, StringBuilder::append);