Java OCA OCP Practice Question 2137

Question

Given the following code:. 

import java.util.regex.Pattern;
public class Main {
 public static void main(String[] args) {
   String[] regexes = {//  w w w . jav a 2  s .  c o m
     "(-|+)\\d+",    "(-|+)?\\d+", "(-|\\+)\\d+",   // 0, 1, 2
     "(-|\\+)?\\d+", "[-+]?\\d+",  "[-+]?[0-9]+",   // 3, 4, 5
     "[-\\+]?\\d+" };                                  // 6
   // (1) INSERT DECLARATION STATEMENT HERE

   System.out.println(Pattern.matches(regexes[i], "2007"));
   System.out.println(Pattern.matches(regexes[i], "-2007"));
   System.out.println(Pattern.matches(regexes[i], "+2007"));
 }
}

Which declarations, when inserted independently at (1), will make the program print:. 

true
true
true

Select the four correct answers.

  • (a) int i = 0;
  • (b) int i = 1;
  • (c) int i = 2;
  • (d) int i = 3;
  • (e) int i = 4;
  • (f) int i = 5;
  • (g) int i = 6;


(d), (e), (f), and (g)

Note

(a), (b) A java.util.regex.PatternSyntaxException is thrown because the first + in the regex is a dangling metacharacter.

(c) The regex does not match the target "2007", since a sign is required.

The regex (-|\\+)? and [-+]? are equivalent: 0 or 1 occurrence of either - or +.

Note that in the [] regex notation, the + sign is an ordinary character as in (e) and (f), and escaping it as in (g) is not necessary.

The metacharacter \d is equivalent to [0-9], i.e., any digit.




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