What is the function of << (two Less than) in Java?

Question

I have the following method:

private static String encode(long number){
    StringBuilder builder = new StringBuilder();
    number = number  < 0 ? ~(number << 1) : number << 1;
    while (number >= 0x20) {
        builder.append(Character.toChars((int) ((0x20 | (number & 0x1f)) + 63)));
        number >>= 5;
    }
    builder.append(Character.toChars((int) (number + 63)));
    return builder.toString();
}

I would like help to try to understand the following parts:

number = number < 0 ? ~ (number << 1) number << 1;

((0x20 | (number & 0x1f)) + 63)