Java OCA OCP Practice Question 2144

Question

What will the program print when compiled and run? 

public class Main {
 public static void main(String[] args) {
    matchMaker("X.*z", "XyzXyz Xz");   // (1)
    matchMaker("X.+z", "XyzXyz Xz");   // (2)
    matchMaker("X.*?z", "XyzXyz Xz");  // (3)
    matchMaker("X.+?z", "XyzXyz Xz");  // (4)
  }/* ww  w. ja  v  a  2  s  . com*/

  public static void matchMaker(String regStr, String target) {
    Matcher matcher = Pattern.compile(regStr).matcher(target);
    System.out.print("|");
    while(matcher.find()) {
      System.out.print(matcher.group() + "|");
    }
    System.out.println();
  }
}

Select the one correct answer. 

(a)  |Xyz|Xyz|Xz|//from   ww w  . j  a  va 2s .com
     |XyzXyz|Xz|
     |Xyz|Xyz|Xz|
     |Xyz|Xyz|
(b)  |XyzXyz Xz|
     |XyzXyz Xz|
     |Xyz|Xyz|Xz|
     |Xyz|Xyz|
(c)  |XyzXyz Xz|
     |XyzXyz|Xz|
     |XyzXyz Xz|
     |XyzXyz|Xz|
(d) The program will throw an exception when run.



(b)

Note

The application of a* and a+ is greedy in (1) and (2).

A greedy quantifier reads the whole target string and backtracks to match as much of the input as possible.

The application of a*? and a+? is reluctant in (3) and (4).

A reluctant quantifier only reads enough of the input to match the regular expression.

The substring Xz is not matched by X.+?z, as it requires non-empty input between X and z.




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