public static boolean isChinese(char c) {
    Character.UnicodeBlock ub = Character.UnicodeBlock.of(c);
    if (ub == Character.UnicodeBlock.CJK_UNIFIED_IDEOGRAPHS
            || ub == Character.UnicodeBlock.CJK_COMPATIBILITY_IDEOGRAPHS
            || ub == Character.UnicodeBlock.CJK_UNIFIED_IDEOGRAPHS_EXTENSION_A
            || ub == Character.UnicodeBlock.GENERAL_PUNCTUATION
            || ub == Character.UnicodeBlock.CJK_SYMBOLS_AND_PUNCTUATION
            || ub == Character.UnicodeBlock.HALFWIDTH_AND_FULLWIDTH_FORMS) {
        return true;
    }
    return false;
}

private static Pattern messyCodeChar = Pattern.compile("\\s*|\t*|\r*|\n*");;
public static boolean isMessyCode(String strName) {

    Pattern p = messyCodeChar;
    Matcher m = p.matcher(strName);
    String after = m.replaceAll("");
    String temp = after.replaceAll("\\p{P}", "");
    char[] ch = temp.trim().toCharArray();
    float chLength = ch.length;
    float count = 0;
    for (int i = 0; i < ch.length; i++) {
        char c = ch[i];
        if (!Character.isLetterOrDigit(c)) {

            if (!isChinese(c)) {
                count = count + 1;
                System.out.print(c);
            }
        }
    }
    float result = count / chLength;
    if (result > 0.4) {
        return true;
    } else {
        return false;
    }

}

java 判斷是否是亂碼（轉.:抱歉忘記出處....................）