How to use methods when objects stored in a linked list?
Hi friend:
I stored a series of objects of certain class inside a linked list. When I get one of them out of the list, I want to use the instance method associated with this object. However, the complier only allow me to treat this object as general object, ( of Object Class), as a result I can't use instance methods which are associated with this object. Can someone tell me how to use the methods associated with the objects which are stored inside a linked list?
Here is my code:
import java.util.*;
public class QueueW
LinkedList qList;
public QueueW(Collection s) //Constructor of QuequW Class
qList = new LinkedList(s); //Declare an object linked list
public void addWaiting(WaitingList w)
boolean result = qList.isEmpty(); //true if list contains no elements
if (result)
qList.addFirst(w);
else
qList.add(w);
public int printCid()
Object d = qList.getFirst(); // the complier doesn't allow me to treat d as a object of waitingList class
int n = d.getCid(); // so I use "Object d"
return n; // yet object can't use getCid() method, so I got error in "int n = d.getCid()"
public void removeWaiting(WaitingList w)
qList.removeFirst();
class WaitingList
int cusmNo;
String cusmName;
int cid;
private static int id_count = 0;
/* constructor */
public WaitingList(int c, String cN)
cusmNo = c;
cusmName = cN;
cid = ++id_count;
public int getCid() //this is the method I want to use
return cid;
Use casting. In other words, cat the object taken from the collection to the correct type and call your method.
HashMap map = /* ... */;
map.put(someKey, myObject);
((MyClass)(map.get(someKey)).myMethod();Chuck
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