[java] How to implement a SQL like 'LIKE' operator in java?

public static boolean like(String source, String exp) {
        if (source == null || exp == null) {
            return false;
        }

        int sourceLength = source.length();
        int expLength = exp.length();

        if (sourceLength == 0 || expLength == 0) {
            return false;
        }

        boolean fuzzy = false;
        char lastCharOfExp = 0;
        int positionOfSource = 0;

        for (int i = 0; i < expLength; i++) {
            char ch = exp.charAt(i);

            // ????
            boolean escape = false;
            if (lastCharOfExp == '\\') {
                if (ch == '%' || ch == '_') {
                    escape = true;
                    // System.out.println("escape " + ch);
                }
            }

            if (!escape && ch == '%') {
                fuzzy = true;
            } else if (!escape && ch == '_') {
                if (positionOfSource >= sourceLength) {
                    return false;
                }

                positionOfSource++;// <<<----- ???1
            } else if (ch != '\\') {// ????,?????????
                if (positionOfSource >= sourceLength) {// ?????source????
                    return false;
                }

                if (lastCharOfExp == '%') { // ??????%,?????
                    int tp = source.indexOf(ch);
                    // System.out.println("?????=%,?????=" + ch + ",position=" + position + ",tp=" + tp);

                    if (tp == -1) { // ????????,????
                        return false;
                    }

                    if (tp >= positionOfSource) {
                        positionOfSource = tp + 1;// <<<----- ????

                        if (i == expLength - 1 && positionOfSource < sourceLength) { // exp??????????,????source?????????
                            return false;
                        }
                    } else {
                        return false;
                    }
                } else if (source.charAt(positionOfSource) == ch) {// ????????ch??
                    positionOfSource++;
                } else {
                    return false;
                }
            }

            lastCharOfExp = ch;// <<<----- ??
            // System.out.println("?????=" + ch + ",position=" + position);
        }

        // expr???????,???????,??source???????????source???
        if (!fuzzy && positionOfSource < sourceLength) {
            // System.out.println("?????=" + lastChar + ",position=" + position );

            return false;
        }

        return true;// ????true
    }

Assert.assertEquals(true, like("abc_d", "abc\\_d"));
        Assert.assertEquals(true, like("abc%d", "abc\\%%d"));
        Assert.assertEquals(false, like("abcd", "abc\\_d"));

        String source = "1abcd";
        Assert.assertEquals(true, like(source, "_%d"));
        Assert.assertEquals(false, like(source, "%%a"));
        Assert.assertEquals(false, like(source, "1"));
        Assert.assertEquals(true, like(source, "%d"));
        Assert.assertEquals(true, like(source, "%%%%"));
        Assert.assertEquals(true, like(source, "1%_"));
        Assert.assertEquals(false, like(source, "1%_2"));
        Assert.assertEquals(false, like(source, "1abcdef"));
        Assert.assertEquals(true, like(source, "1abcd"));
        Assert.assertEquals(false, like(source, "1abcde"));

        // ????case?????
        Assert.assertEquals(true, like(source, "_%_"));
        Assert.assertEquals(true, like(source, "_%____"));
        Assert.assertEquals(true, like(source, "_____"));// 5?
        Assert.assertEquals(false, like(source, "___"));// 3?
        Assert.assertEquals(false, like(source, "__%____"));// 6?
        Assert.assertEquals(false, like(source, "1"));

        Assert.assertEquals(false, like(source, "a_%b"));
        Assert.assertEquals(true, like(source, "1%"));
        Assert.assertEquals(false, like(source, "d%"));
        Assert.assertEquals(true, like(source, "_%"));
        Assert.assertEquals(true, like(source, "_abc%"));
        Assert.assertEquals(true, like(source, "%d"));
        Assert.assertEquals(true, like(source, "%abc%"));
        Assert.assertEquals(false, like(source, "ab_%"));

        Assert.assertEquals(true, like(source, "1ab__"));
        Assert.assertEquals(true, like(source, "1ab__%"));
        Assert.assertEquals(false, like(source, "1ab___"));
        Assert.assertEquals(true, like(source, "%"));

        Assert.assertEquals(false, like(null, "1ab___"));
        Assert.assertEquals(false, like(source, null));
        Assert.assertEquals(false, like(source, ""));