This method tells you how many bytes are required to hold the information in a particular String. (Each char in a String is 16 bits, or two bytes, long, to support Unicode characters.) The argument is of type String and is called s.

• 这个方法告诉我们需要多少字节才能容纳一个特定字串里的信息（字串里的每个字符都是16位，或者说2个字节、长整数，以便提供对Unicode字符的支持）。 自变量的类型为String，而且叫作s。