how many bytes does a string object in memory,contains the object header?

Question

As i know,a Java object contains object header,reference and it's data.

//jdk 1.7
public final class String{
       private final char value[];
       private int hash;
       //...
    }

For new String("abc") ,how many bytes will it take if we just think about 32-bit system?

totleBytes = 
    8//String Object header
    +4 //value reference 
    +4 //hash
    +12 //char[] object header
    +3*1//value[] data

does it right,or miss something?