Java StringUtils

public static boolean isEquals(String s1, String s2) {
if (s1 == null && s2 == null)
return true;
if (s1 == null || s2 == null)
return false;
return s1.equals(s2);
}

public static boolean isJavaIdentifier(String s) {
if (s.length() == 0 || !Character.isJavaIdentifierStart(s.charAt(0))) {
return false;
}
for (int i=1; i<s.length(); i++) {
if (!Character.isJavaIdentifierPart(s.charAt(i))) {
return false;
}
}
return true;
}