Suppose you want the user to choose a color from one of the predefined
Java colors,
Color.red
Color.yellow
The traditional solution is tedious:
1. Add strings to a list field
2. When a string was selected, use an if/else/else branch to convert it
to the enum Value.
if (selection.equals("red")) color = Color.red;
else if (selection.equals("yellow")) color = Color.yellow;
else . . .
3. Feel bad for not having set up a hash table instead.
The problem is that color. red is the name of a constant, whereas "red"
is a string object.
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Tip
Use reflection to convert the strings!
Sample usage:
new EnumList(Color.class, new String[] {"red", "yellow", . . .})
The code:
class EnumList extends JList
{ public EnumList(Class cl, String[] labels)
{for (int i = 0; i < Labels.length; i++)
{ String label = labels[i];
int value = 0;
try
{ java.lang.reflect.Field f = cl.getField(label);
value = f.getInt(cl);
}
catch(Exception e)
{ Label = "(" + label + ")";
}
table.put (label, new Integer (value i ));
}
setListData(labels);
setSelectedIndex(0);
}
public int getValue()
{ return ((Integer)table.get(getSelectedValue())).intValue();
}
private Hashtable table = new Hashtable();
}
Note
The drawback of this trick is that it does not work for internationalization.
The enumerated constants are usually in English, but your users may want to
see them in the local language, i.e. rot gelb
