bit manipulation - StringBuilder initialization in Java -

i needed use this method, , after looking @ source code, noticed stringbuilder initialization not familar me (i use no-argument constructor stringbuilder, i.e. new stringbuilder()).

in method:

stringbuilder sb = new stringbuilder(items.size() << 3); 

from javadoc:

java.lang.stringbuilder.stringbuilder(int capacity)

constructs string builder no characters in , initial capacity specified capacity argument.

why bit shift needed here?

source code:

/** creates backslash escaped string, joining items. */   public static string join(list<?> items, char separator) {     stringbuilder sb = new stringbuilder(items.size() << 3);     boolean first=true;     (object o : items) {       string item = o.tostring();       if (first) {         first = false;       } else {         sb.append(separator);       }       (int i=0; i<item.length(); i++) {         char ch = item.charat(i);         if (ch=='\\' || ch == separator) {           sb.append('\\');         }         sb.append(ch);       }     }     return sb.tostring();   } 

bitshift 3 means multiplying 2^3 8. author must have assumed each item take @ 8 characters in resulting string. therefore or initialized stringbuilder capacity run efficiently. if assumption correct stringbuilder not reallocate internal structures.