Generic enum parameter in java. Is this possible?
I am trying to write a generic function that will accept any enum, and put the values into a map for use in a drop down.
This is what I have so far, (for a specific enum), can my function enumToMap be rewritten generally to accept any enum type?
import java.util.ArrayList;
import java.util.Arrays;
import java.util.HashMap;
import java.util.List;
import java.util.Map;
public class Main {
private enum testenum{
RED,BLUE,GREEN
}
private static Map enumToMap(testenum e){
HashMap result = new HashMap();
List<testenum> orderReceiptKeys = Arrays.asList(e.values());
List<String> orderReceiptValues = unCapsCase(orderReceiptKeys);
for(int i=0;i<orderReceiptKeys.size();i++){
result.put(orderReceiptKeys.get(i), orderReceiptValues.get(i));
}
return result;
}
/**
* Converts a string in the form of 'TEST_CASE' to 'Test case'
* @param s
* @return
*/
private static String unCapsCase(String s){
StringBuilder builder = new StringBuilder();
boolean first=true;
for(char c:s.toCharArray()){
if(!first)
c=Character.toLowerCase(c);
if(c=='_')
c=' ';
builder.appen开发者_如何学运维d(c);
first=false;
}
return builder.toString();
}
/**
* Converts a list of strings in the form of 'TEST_CASE' to 'Test case'
* @param l
* @return
*/
private static List<String> unCapsCase(List l){
List<String> list = new ArrayList();
for(Object o:l){
list.add(unCapsCase(o.toString()));
}
return list;
}
public static void main(String[] args) throws Exception {
try{
testenum e=testenum.BLUE;
Map map = enumToMap(e);
for(Object k:map.keySet()){
System.out.println(k.toString()+"=>"+map.get(k));
}
}catch(Exception e){
e.printStackTrace();
}
}
}
Thanks for any suggestions.
Change the signature of your enumToMap
method to something like this:
private static <E extends Enum<E>> Map<E, String> enumToMap(Class<E> enumType)
Then where you call e.values()
use enumType.getEnumConstants()
instead.
In your main method you can then call this method like:
Map<testenum, String> map = enumToMap(testenum.class);
As seanizer mentions, you should also be using EnumMap
as the Map
implementation rather than HashMap
.
Don't use a HashMap with enums, this is what an EnumMap was designed for.
As written in the Map section of the Collection Trail in the Sun Java Tutorial:
EnumMap
, which is internally implemented as an array, is a high-performanceMap
implementation for use with enum keys. This implementation combines the richness and safety of theMap
interface with a speed approaching that of an array. If you want to map an enum to a value, you should always use anEnumMap
in preference to an array.
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