Hashtables not accepting String as key

Question

I don't understand why Eclipse is giving me an error regarding passing the String returned by the BufferedReader into Hashtable's put(Object,Object) method. I've read the API, I don't recognise any clues. Is it perhaps that it cannot be sure that it will return a unique String?

The String dictionary is set elsewhere in the file,I've stripped this down to the bit that matters - the method in question & anything happening with its variables.

import java.io.BufferedReader; import java.io.FileReader; import java.io.IOException; import java.util.Hashtable; public class Model { private Hashtable hash=new Hashtable(); private String dictionary; public void loadWords() throws IOException{ BufferedReader br=null; try{ br=new BufferedReader(new FileReader(dictionary)); do{ hash.put(br.readLine(), new Node<E>); } while(br.readLine()!=null); }catch(IOException iOE){ System.out.println("Fission mailed"); } finally{ br.close(); // Closing the buffered reader } }

Including the error you're seeing would be helpful in formulating an answer. — Simes
– Simes, Commented Oct 13, 2012 at 19:36
Consider: ConcurrentHashMap, Collections.synchronizedMap, try-with-resources, Files.readLines, Files.readAllLines — btiernay
– btiernay, Commented Oct 13, 2012 at 19:57

Subhrajyoti Majumder · Accepted Answer · 2012-10-14 04:18:37Z

4

It looks like it's not problem with key it is problem with value part. You can not add new Node<E> this as a Value. It must have specific type like new Node<String>() or new Node<Integer>().

edited Oct 14, 2012 at 4:18

answered Oct 13, 2012 at 19:36

Subhrajyoti Majumder

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1 Comment

gideonparanoid Over a year ago

Darn, so simple. Eclipe's error warning message really wasn't helping with this & it was staring me in the face. Thanks.

Ярослав Рахматуллин · Accepted Answer · 2012-10-13 19:48:25Z

\1. You are not calling the constructor of node: hash.put(br.readLine(), new Node);

To call the default constructor you have to call the "method" with the name of the class like:

new String(); /*or*/ new Node();

\2. The generic type <E> is not seen anywhere in the declaration of the class. To use that you would have to do something like:

 public class Model<E> { private Hashtable<String, Node<E>> hash=new Hashtable<String, Node<E>> ();

.. so either go all the way or remove it entirely.

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