验证Android用户输入日期

如何验证用户输入的日期是有效还是无效？

private Pattern pattern;
private Matcher matcher;
private static final String DATE_PATTERN =
       "(0?[1-9]|1[012]) [/.-] (0?[1-9]|[12][0-9]|3[01]) [/.-] ((19|20)\\d\\d)";
/**
* Validate date format with regular expression
* @param date date address for validation
* @return true valid date format, false invalid date format
*/
public boolean validate(final String date){
  matcher = pattern.matcher(date);
  if(matcher.matches()){
      matcher.reset();

      if(matcher.find()){
          String day = matcher.group();
          String month = matcher.group();
          int year = Integer.parseInt(matcher.group());

          if (day.equals("") &&
           (month.equals("") || month .equals("") || month.equals("") ||
                   month.equals("") || month.equals("") || month .equals("") ||
                   month.equals(""))) {
             return false; // only 1,3,5,7,8,10,12 has 31 days
          }
      }
      else{
           return false;
      }
  }
  else{
      return false;
  }
}

private Pattern pattern;
private Matcher matcher;

private static final String DATE_PATTERN =
       "(0?[1-9]|1[012]) [/.-] (0?[1-9]|[12][0-9]|3[01]) [/.-] ((19|20)\\d\\d)";

  /**
   * Validate date format with regular expression
   * @param date date address for validation
   * @return true valid date format, false invalid date format
   */
public boolean validate(final String date){

  matcher = pattern.matcher(date);

  if(matcher.matches()){
      matcher.reset();

      if(matcher.find()){
          String day = matcher.group();
          String month = matcher.group();
          int year = Integer.parseInt(matcher.group());

          if (day.equals("") &&
            (month.equals("") || month .equals("") || month.equals("") ||
                   month.equals("") || month.equals("") || month .equals("") ||
                   month.equals(""))) {
             return false; // only 1,3,5,7,8,10,12 has 31 days
          } 

          else if (month.equals("") || month.equals("")) {
               //leap year
               if(year % ==){
                   if(day.equals("") || day.equals("")){
                       return false;
                   }
                   else{
                       return true;
                   }
              }
              else{
                  if(day.equals("")||day.equals("")||day.equals("")){
                      return false;
                  }
                  else{
                      return true;
                  }
              }
          }

          else{
              return true;
          }
      }

      else{
           return false;
      }
  }
  else{
      return false;
  }
}

再将下面的代码放到onClick()中：

matcher = Pattern.compile(DATE_PATTERN).matcher(Birthday);

//Birthday validator
    else if (!matcher.matches()) {
    Toast.makeText(getApplicationContext(), "Invalid Birthday!", Toast.LENGTH_SHORt).show();
}