public static boolean isMixedCase(final CharSequence cs) {
        if (N.isNullOrEmpty(cs) || cs.length() == 1) {
            return false;
        }

        boolean containsUppercase = false;
        boolean containsLowercase = false;
        final int len = cs.length();

        if (cs.getClass().equals(String.class)) {
            final char[] chars = getCharsForReadOnly((String) cs);

            for (int i = 0; i < len; i++) {
                if (containsUppercase && containsLowercase) {
                    return true;
                } else if (Character.isUpperCase(chars[i])) {
                    containsUppercase = true;
                } else if (Character.isLowerCase(chars[i])) {
                    containsLowercase = true;
                }
            }
        } else {
            for (int i = 0; i < len; i++) {
                if (containsUppercase && containsLowercase) {
                    return true;
                } else if (Character.isUpperCase(cs.charAt(i))) {
                    containsUppercase = true;
                } else if (Character.isLowerCase(cs.charAt(i))) {
                    containsLowercase = true;
                }
            }
        }

        return containsUppercase && containsLowercase;
    }
public static boolean isMixedCase ( final CharSequence cs ) { if ( N . isNullOrEmpty ( cs ) || cs . length ( ) == 1 ) { return false ; } boolean containsUppercase = false ; boolean containsLowercase = false ; final int len = cs . length ( ) ; if ( cs . getClass ( ) . equals ( String . class ) ) { final char [ ] chars = getCharsForReadOnly ( ( String ) cs ) ; for ( int i = 0 ; i < len ; i ++ ) { if ( containsUppercase && containsLowercase ) { return true ; } else if ( Character . isUpperCase ( chars [ i ] ) ) { containsUppercase = true ; } else if ( Character . isLowerCase ( chars [ i ] ) ) { containsLowercase = true ; } } } else { for ( int i = 0 ; i < len ; i ++ ) { if ( containsUppercase && containsLowercase ) { return true ; } else if ( Character . isUpperCase ( cs . charAt ( i ) ) ) { containsUppercase = true ; } else if ( Character . isLowerCase ( cs . charAt ( i ) ) ) { containsLowercase = true ; } } } return containsUppercase && containsLowercase ; }
Copied from Apache Commons Lang: StringUtils#isMixedCase.

@param cs
@return