java - What are variables "offset" & "hash" in String.hashCode()?

Question

I've read that this is the source code for String.hashCode()

   public int hashCode() {
   int h = hash;
   if (h == 0) {
       int off = offset;
       char val[] = value;
       int len = count;

       for (int i = 0; i < len; i++) {
           h = 31*h + val[off++];
       }
       hash = h;
   }
   return h;
   }

My question is, what are "offset" & "hash"? I can tell that "value" is the actual String and "length" is its length, but I don't understand what the other two are.

Answer 1

The offset is the first index of the value[] array of chars of the String. The hash variable is a field for caching the hashCode so as to be more efficient (the hashCode() method only computes the hash if it's current value is 0; else it returns the cached hash)