Cloning a Hashtable

[bhuvan gupta]

the java documentation says :
Hashtable.clone() Creates a shallow copy of this hashtable. The keys and values themselves are not cloned. This is a relatively expensive operation.
What do u mean by shallow copy ?? Is it just means creating a new reference of the object or something more ??

[Frank Carver]

A shallow copy in this case is a new hashtable, with one entry for each entry in the original hashtable, but the entries refer to the same keys and values as the original hashtable.
for example, consider this sequence:

class Temp
{
  public String value;
  public String toString() { return value; }
}
 
Temp temp = new Temp();
temp.value = "xxx";
Hashtable a = new Hashtable();
a.put("Temp", temp);
System.out.println(a.get("Temp"));  // gives "xxx"
 
Hashtable b = a.clone();
System.out.println(b.get("Temp"));  // gives "xxx"
 
// both Hashtables refer to the same Temp object, so they both change
temp.value = "yyy";
System.out.println(a.get("Temp"));  // gives "yyy"
System.out.println(b.get("Temp"));  // gives "yyy"

[bhuvan gupta]

Got the funda
Thank you very much Frank