It was a sunny day with easy code and birds singing. But, suddenly a static HashMap (it could be non-static, also) wants to be copied into a two column JTable, keys on first column, and values on the second one. Well, the clouds start to press and before I notice it starts to rain … "with questions":

• How to delete all rows of a JTable (I need this because sometimes I have to refresh the JTable for 0) ?
• How to obtain the keys from the JTable by index, or similar?
• How to add or insert the HashMap elements into JTable ?

Oh, sorry, I forgot to introduce you my static HashMap, nothing special, just a trivial one – the elements are irrelevant, therefore I’ll skip it:

public class MyMapHostClass {
...
public static Map myMap = new HashMap();
...
}

Afterwards, it proves to be a summer rain, warm and refreshing, because the answers jump up in a few minutes: delete all rows using a backward loop (or a nice trick) – both here, get all keys with the keySet method, and insert/add them into JTable with insertRow/addRow method. Well, I glue all these answers into lines code, and get this:

...
DefaultTableModel  model = (DefaultTableModel) jTable.getModel();
...
//remove all rows
model.getDataVector().removeAllElements();
...
//get all keys – notice the static effect, you can use it for non-static HashMap either
Set keys = MyMapHostClass.myMap.keySet();

//get an Iterator over keys
Iterator iteratorKeys = keys.iterator();

//put them into jTable
while (iteratorKeys.hasNext()) {
     String key = (String) iteratorKeys.next();
     //insert on first position by pushing down the existing rows
     model.insertRow(0, new Object[]{key, MyMapHostClass.myMap.get(key)});
     //append at the end
     model.addRow(new Object[]{key, MyMapHostClass.myMap.get(key)});
     }

Done! Now, is still raining, but … I’m singing in the rain!

From http://e-blog-java.blogspot.com/2011/03/how-to-copy-static-hashmap-into-jtable.html