Hash Table - Using a Separate Class, and also Objects

Usually - and particularly for your dossier, most likely - you will be making a hash table of objects, i.e. of instances of one of your "template" classes.

Also usually - and for your master aspects - you will use a separate class for the hash table.

And you'll usually use a GUI interface too.

So here's an example with the way you will usually implement a hash table.

******* But what is missing from this example is tie-breaking. ******* See the full example for that.

     

 

/Users/adelaide/Public/Netbeans - All JSR Projects/Hashing 2012/src/hashing2012package/HashGUI.java

  1 package hashing2012package;
  2 
  3 /**
  4  *
  5  * @author John Rayworth
  6  */
  7 public class HashGUI extends javax.swing.JFrame {
  8 
  9     HashTable myHashTable = new HashTable();
 10 
 11     public HashGUI() {
 12         initComponents();
 13     }
 14 
246 
247     private void addButtonMouseReleased(java.awt.event.MouseEvent evt) {
248         
249         LibraryBook book = new LibraryBook(bookTitleTF.getText(), Double.parseDouble(DDNumberTF.getText()));
250         myHashTable.addToHashTable(book);
251         bookTitleTF.setText("");
252         DDNumberTF.setText("");
253         
254     }
255 
256     private void searchButtonMouseReleased(java.awt.event.MouseEvent evt) {
257         
258         LibraryBook bookResult = new LibraryBook();
259         try {
260             bookResult = myHashTable.findName(bookSearchTF.getText());
261         } catch (Exception e) {
262             System.out.println(e.getStackTrace());
263         }
264         DDNumberResultTF.setText(bookResult.getDDNumber()+"");
265         
266     }

 

 

/Users/adelaide/Public/Netbeans - All JSR Projects/Hashing 2012/src/hashing2012package/HashTable.java

 2 package hashing2012package;
 3 
 4 /**
 5  *
 6  * @author John Rayworth
 7  */
 8 public class HashTable {
 9     
10     
11     private LibraryBook[] hashArray = new LibraryBook [5000];
12     
13     
14     public void addToHashTable(LibraryBook bookToHash){
15         int total = 0;
16         String nameToHash = bookToHash.getBookTitle();
17         for(int i = 0; i < nameToHash.length(); i++){
18             total += nameToHash.charAt(i);
19         }
20         int hashValue = total % 5000;
21         hashArray[hashValue] = bookToHash;  
22     }
23     
24     
25     public LibraryBook findName(String stringToFind) throws Exception{
26         int total = 0;
27         for(int i = 0; i < stringToFind.length(); i++){
28             total += stringToFind.charAt(i);
29         }
30         int hashValue = total % 5000;
31         
32         Exception e = new Exception();
33         if(hashArray[hashValue] == null){
34             throw e;
35         }else{
36             return hashArray[hashValue];
37         }
38 
39     }
40     
41 }

Scorll down if you think you need to see the LibraryBook template class.

 

 

 

 

 

/Users/adelaide/Public/Netbeans - All JSR Projects/Hashing 2012/src/hashing2012package/LibraryBook.java

 1 package hashing2012package;
 2 
 3 /**
 4  *
 5  * @author John Rayworth
 6  */
 7 public class LibraryBook {
 8     
 9     
10    private String bookTitle = "not set yet";
11    private double DDNumber = -999.999;
12     
13    public LibraryBook(){
14        
15    }
16    
17    public LibraryBook(String bookTitle, double DDNumber){
18        this.bookTitle = bookTitle;
19        this.DDNumber = DDNumber;
20    }
21    
22    public String getBookTitle(){
23        return bookTitle;
24    }
25    
26    public double getDDNumber(){
27        return DDNumber;
28    }
29    
30    public void setBookTitle(String bookTitle){
31        this.bookTitle = bookTitle;
32    }
33    
34    public void setDDNumber(double DDNumber){
35        this.DDNumber = DDNumber;
36    }
37  
38 }
39 
40