Mutable, Immutable, and Cloneable Objects - Data Structures and Abstractions with Java - page 796

protected Object clone()
{

Node theCopy = null ;
try
{

theCopy = (Node) super .clone();

}
catch (CloneNotSupportedException e)
{

throw new Error(e.toString());

}
theCopy.data = (T)data.clone();
theCopy.next = null ; // don't clone link; it's set later

return theCopy;
} // end clone
} // end Node

Remember that data invokes a public method clone that does not throw an exception, and so
data.clone() can appear outside of a try block.

30.26

Cloning the chain. LList 's clone method invokes super.clone() in a statement such as

LList<T> theCopy = (LList<T>) super .clone();

The method then must clone the chain of nodes that stores the list's data. To do so, the method
needs to traverse the chain, clone each node, and link the cloned nodes appropriately. We begin by
cloning the first node so that we can set the data field firstNode correctly:

// make a copy of the first node
theCopy.firstNode = (Node)firstNode.clone();

Next, we traverse the rest of the chain. A reference newRef references the last node that we
have added to the new chain, while the reference oldRef keeps track of where we are in the tra-
versal of the original chain. The statement

newRef.setNextNode((Node)oldRef.clone()); // attach cloned node

clones the current node in the original chain, along with its data, and then links the clone to the end
of the new chain. Recall that Node 's clone method also clones the data that a node references.
The following statements incorporate the previous ideas and clone the rest of the chain:

Node newRef = theCopy.firstNode; // last node in new chain
Node oldRef = firstNode.getNextNode(); // next node in old chain
for ( int count = 2; count <= numberOfEntries; count++)
{

newRef.setNextNode((Node)oldRef.clone()); // attach cloned node
newRef = newRef.getNextNode(); // update references

oldRef = oldRef.getNextNode();
} // end for

30.27

The code in the previous segment assumes a nonempty chain of nodes. The complete clone method
that follows checks for an empty chain.

public Object clone()
{

LList<T> theCopy = null ;