StringUtil Class — netty Architecture

Source Code

common/src/main/java/io/netty/util/internal/StringUtil.java lines 29–730

public final class StringUtil {

    public static final String EMPTY_STRING = "";
    public static final String NEWLINE = SystemPropertyUtil.get("line.separator", "\n");

    public static final char DOUBLE_QUOTE = '\"';
    public static final char COMMA = ',';
    public static final char LINE_FEED = '\n';
    public static final char CARRIAGE_RETURN = '\r';
    public static final char TAB = '\t';
    public static final char SPACE = 0x20;

    private static final String[] BYTE2HEX_PAD = new String[256];
    private static final String[] BYTE2HEX_NOPAD = new String[256];
    private static final byte[] HEX2B;

    /**
     * 2 - Quote character at beginning and end.
     * 5 - Extra allowance for anticipated escape characters that may be added.
     */
    private static final int CSV_NUMBER_ESCAPE_CHARACTERS = 2 + 5;
    private static final char PACKAGE_SEPARATOR_CHAR = '.';

    static {
        // Generate the lookup table that converts a byte into a 2-digit hexadecimal integer.
        for (int i = 0; i < BYTE2HEX_PAD.length; i++) {
            String str = Integer.toHexString(i);
            BYTE2HEX_PAD[i] = i > 0xf ? str : ('0' + str);
            BYTE2HEX_NOPAD[i] = str;
        }
        // Generate the lookup table that converts an hex char into its decimal value:
        // the size of the table is such that the JVM is capable of save any bounds-check
        // if a char type is used as an index.
        HEX2B = new byte[Character.MAX_VALUE + 1];
        Arrays.fill(HEX2B, (byte) -1);
        HEX2B['0'] = 0;
        HEX2B['1'] = 1;
        HEX2B['2'] = 2;
        HEX2B['3'] = 3;
        HEX2B['4'] = 4;
        HEX2B['5'] = 5;
        HEX2B['6'] = 6;
        HEX2B['7'] = 7;
        HEX2B['8'] = 8;
        HEX2B['9'] = 9;
        HEX2B['A'] = 10;
        HEX2B['B'] = 11;
        HEX2B['C'] = 12;
        HEX2B['D'] = 13;
        HEX2B['E'] = 14;
        HEX2B['F'] = 15;
        HEX2B['a'] = 10;
        HEX2B['b'] = 11;
        HEX2B['c'] = 12;
        HEX2B['d'] = 13;
        HEX2B['e'] = 14;
        HEX2B['f'] = 15;
    }

    private StringUtil() {
        // Unused.
    }

    /**
     * Get the item after one char delim if the delim is found (else null).
     * This operation is a simplified and optimized
     * version of {@link String#split(String, int)}.
     */
    public static String substringAfter(String value, char delim) {
        int pos = value.indexOf(delim);
        if (pos >= 0) {
            return value.substring(pos + 1);
        }
        return null;
    }

    /**
     * Get the item before one char delim if the delim is found (else null).
     * This operation is a simplified and optimized
     * version of {@link String#split(String, int)}.
     */