validate base64string

gistfile1.java

static final Pattern pattern = Pattern.compile("^(?:[A-Za-z0-9+/]{4})*(?:[A-Za-z0-9+/]{2}==|[A-Za-z0-9+/]{3}=)?$");

public static boolean isBase642(String base64) { 
  final Matcher m = pattern.matcher(base64); 
  return m.matches(); 
}

        
// with guava   
// this is not really correct as = should only be allowed in the end 
static final CharMatcher base64Chars = CharMatcher.inRange('a', 'z').or(CharMatcher.inRange('A', 'Z')).or(CharMatcher.WHITESPACE).or(CharMatcher.DIGIT).or(CharMatcher.is('=') );

public static boolean isBase64(String base64) { 
        return base64Chars.matchesAllOf(base64); 
}