這有個工具類可以判斷字串的：來自Blankj的專案

 private static boolean isSpace(final String s) {
        if (s == null) return true;
        for (int i = 0, len = s.length(); i < len; ++i) {
            if (!Character.isWhitespace(s.charAt(i))) {
                return false;
            }
        }
        return true;
    }
 

 /**
     * Determines if the specified character is white space according to Java.
     * A character is a Java whitespace character if and only if it satisfies
     * one of the following criteria:
     * <ul>
     * <li> It is a Unicode space character ({@code SPACE_SEPARATOR},
     *      {@code LINE_SEPARATOR}, or {@code PARAGRAPH_SEPARATOR})
     *      but is not also a non-breaking space ({@code '\u005Cu00A0'},
     *      {@code '\u005Cu2007'}, {@code '\u005Cu202F'}).
     * <li> It is {@code '\u005Ct'}, U+0009 HORIZONTAL TABULATION.
     * <li> It is {@code '\u005Cn'}, U+000A LINE FEED.
     * <li> It is {@code '\u005Cu000B'}, U+000B VERTICAL TABULATION.
     * <li> It is {@code '\u005Cf'}, U+000C FORM FEED.
     * <li> It is {@code '\u005Cr'}, U+000D CARRIAGE RETURN.
     * <li> It is {@code '\u005Cu001C'}, U+001C FILE SEPARATOR.
     * <li> It is {@code '\u005Cu001D'}, U+001D GROUP SEPARATOR.
     * <li> It is {@code '\u005Cu001E'}, U+001E RECORD SEPARATOR.
     * <li> It is {@code '\u005Cu001F'}, U+001F UNIT SEPARATOR.
     * </ul>
     *
     * <p><b>Note:</b> This method cannot handle <a
     * href="#supplementary"> supplementary characters</a>. To support
     * all Unicode characters, including supplementary characters, use
     * the {@link #isWhitespace(int)} method.
     *
     * @param   ch the character to be tested.
     * @return  {@code true} if the character is a Java whitespace
     *          character; {@code false} otherwise.
     * @see     Character#isSpaceChar(char)
     * @since   1.1
     */
    public static boolean isWhitespace(char ch) {
        return isWhitespace((int)ch);
    }

    /**
     * Determines if the specified character (Unicode code point) is
     * white space according to Java.  A character is a Java
     * whitespace character if and only if it satisfies one of the
     * following criteria:
     * <ul>
     * <li> It is a Unicode space character ({@link #SPACE_SEPARATOR},
     *      {@link #LINE_SEPARATOR}, or {@link #PARAGRAPH_SEPARATOR})
     *      but is not also a non-breaking space ({@code '\u005Cu00A0'},
     *      {@code '\u005Cu2007'}, {@code '\u005Cu202F'}).
     * <li> It is {@code '\u005Ct'}, U+0009 HORIZONTAL TABULATION.
     * <li> It is {@code '\u005Cn'}, U+000A LINE FEED.
     * <li> It is {@code '\u005Cu000B'}, U+000B VERTICAL TABULATION.
     * <li> It is {@code '\u005Cf'}, U+000C FORM FEED.
     * <li> It is {@code '\u005Cr'}, U+000D CARRIAGE RETURN.
     * <li> It is {@code '\u005Cu001C'}, U+001C FILE SEPARATOR.
     * <li> It is {@code '\u005Cu001D'}, U+001D GROUP SEPARATOR.
     * <li> It is {@code '\u005Cu001E'}, U+001E RECORD SEPARATOR.
     * <li> It is {@code '\u005Cu001F'}, U+001F UNIT SEPARATOR.
     * </ul>
     * <p>
     *
     * @param   codePoint the character (Unicode code point) to be tested.
     * @return  {@code true} if the character is a Java whitespace
     *          character; {@code false} otherwise.
     * @see     Character#isSpaceChar(int)
     * @since   1.5
     */
    public static boolean isWhitespace(int codePoint) {
        // We don't just call into icu4c because of the JNI overhead. Ideally we'd fix that.
        // Any ASCII whitespace character?
        if ((codePoint >= 0x1c && codePoint <= 0x20) || (codePoint >= 0x09 && codePoint <= 0x0d)) {
            return true;
        }
        if (codePoint < 0x1000) {
            return false;
        }
        // OGHAM SPACE MARK or MONGOLIAN VOWEL SEPARATOR?
        if (codePoint == 0x1680 || codePoint == 0x180e) {
            return true;
        }
        if (codePoint < 0x2000) {
            return false;
        }
        // Exclude General Punctuation's non-breaking spaces (which includes FIGURE SPACE).
        if (codePoint == 0x2007 || codePoint == 0x202f) {
            return false;
        }
        if (codePoint <= 0xffff) {
            // Other whitespace from General Punctuation...
            return codePoint <= 0x200a || codePoint == 0x2028 || codePoint == 0x2029 || codePoint == 0x205f ||
                codePoint == 0x3000; // ...or CJK Symbols and Punctuation?
        }
        // Let icu4c worry about non-BMP code points.
        return isWhitespaceImpl(codePoint);
    }

    native static boolean isWhitespaceImpl(int codePoint);