Review Questions

10.16	Which of the following operators cannot be used in conjunction with a `String` object? Select the two correct answers. `+` `-` `+=` `.` `&`
10.17	Which expression will extract the substring `"kap"` from a string defined by `String str = "kakapo"`? Select the one correct answer. `str.substring(2, 2)` `str.substring(2, 3)` `str.substring(2, 4)` `str.substring(2, 5)` `str.substring(3, 3)`
10.18	What will be the result of attempting to compile and run the following code? class MyClass { public static void main(String[] args) { String str1 = "str1"; String str2 = "str2"; String str3 = "str3"; str1.concat(str2); System.out.println(str3.concat(str1)); } } Select the one correct answer. The code will fail to compile since the expression `str3.concat(str1)` will not result in a valid argument for the `println()` method. The program will print `str3str1str2` when run. The program will print `str3` when run. The program will print `str3str1` when run. The program will print `str3str2` when run.
10.19	What function does the `trim()` method of the `String` class perform? Select the one correct answer. It returns a string where the leading white space of the original string has been removed. It returns a string where the trailing white space of the original string has been removed. It returns a string where both the leading and trailing white space of the original string has been removed. It returns a string where all the white space of the original string has been removed. None of the above.
10.20	Which statements are true? Select the two correct answers. `String` objects are immutable. Subclasses of the `String` class can be mutable. All wrapper classes are declared `final`. All objects have a `public` method named `clone()`. The expression `((new StringBuffer()) instanceof String)` is always `true`.
10.21	Which of these expressions are legal? Select the four correct answers. `"co".concat("ol")` `("co" + "ol")` `('c' + 'o' + 'o' + 'l')` `("co" + new String('o' + 'l'))` `("co" + new String("co"))`
10.22	What will be the result of attempting to compile and run the following code? public class RefEq { public static void main(String[] args) { String s = "ab" + "12"; String t = "ab" + 12; String u = new String("ab12"); System.out.println((s==t) + " " + (s==u)); } } Select the one correct answer. The code will fail to compile. The program will print `false false` when run. The program will print `false true` when run. The program will print `true false` when run. The program will print `true true` when run.
10.23	Which of these parameter lists have a corresponding constructor in the `String` class? Select the three correct answers. `()` `(int capacity)` `(char[] data)` `(String str)`
10.24	Which method is not defined in the `String` class? Select the one correct answer. `trim()` `length()` `concat(String)` `hashCode()` `reverse()`
10.25	Which statement concerning the `charAt()` method of the `String` class is true? Select the one correct answer. The `charAt()` method takes a `char` value as an argument. The `charAt()` method returns a `Character` object. The expression `("abcdef").charAt(3)` is illegal. The expression `"abcdef".charAt(3)` evaluates to the character `'d'`. The index of the first character is 1.
10.26	Which expression will evaluate to `true`? Select the one correct answer. `"hello: there!".equals("hello there")` `"HELLO THERE".equals("hello there")` `("hello".concat("there")).equals("hello there")` `"Hello There".compareTo("hello there") == 0` `"Hello there".toLowerCase().equals("hello there")`
10.27	What will the following program print when run? public class Search { public static void main(String[] args) { String s = "Contentment!"; int middle = s.length()/2; String nt = s.substring(middle-1, middle+1); System.out.println(s.lastIndexOf(nt, middle)); } }; Select the one correct answer. `2` `4` `5` `7` `9` `11`