? Matches zero or one occurrences of the preceding pattern : Regex « Utility Classes « SCJP

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SCJP » Utility Classes » Regex 
8.24.8.? Matches zero or one occurrences of the preceding pattern
public class MainClass{
  public static void main(String[] argv){
    String str = "ababc";
    
    
    System.out.println(str.split("(ab)?").length);
  }
}
 
4
8.24.Regex
8.24.1.. Matches any character
8.24.2.\d Matches any digit ("0" - "9")
8.24.3.\s Matches any whitespace character, such as space, tab, or newline
8.24.4.\w Matches any letter ("a" - "z" or "A" - "Z") or digit
8.24.5.Using escape sequence in regular expression.
8.24.6.* Matches zero or more occurrences of the preceding pattern
8.24.7.+ Matches one or more occurrences of the preceding pattern
8.24.8.? Matches zero or one occurrences of the preceding pattern
8.24.9.Flags for regex
8.24.10.A small program that uses a console to support testing another class
8.24.11.Tokenizing with String.split()
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