Java: Generics, Class.isaAssignableFrom, and type casting
- by bguiz
This method that uses method-level generics, that parses the values from a custom POJO, JXlistOfKeyValuePairs (which is exactly that). The only thing is that both the keys and values in JXlistOfKeyValuePairs are Strings.
This method wants to taken in, in addition to the JXlistOfKeyValuePairs instance, a Class<T> that defines which data type to convert the values to (assume that only Boolean, Integer and Float are possible). It then outputs a HashMap with the specified type for the values in its entries.
This is the code that I have got, and it is obviously broken.
private <T extends Object> Map<String, T>
fromListOfKeyValuePairs(JXlistOfKeyValuePairs jxval, Class<T> clasz)
{
Map<String, T> val = new HashMap<String, T>();
List<Entry> jxents = jxval.getEntry();
T value;
String str;
for (Entry jxent : jxents)
{
str = jxent.getValue();
value = null;
if (clasz.isAssignableFrom(Boolean.class))
{
value = (T)(Boolean.parseBoolean(str));
} else if (clasz.isAssignableFrom(Integer.class))
{
value = (T)(Integer.parseInt(str));
} else if (clasz.isAssignableFrom(Float.class))
{
value = (T)(Float.parseFloat(str));
}
else {
logger.warn("Unsupporteded value type encountered in key-value pairs, continuing anyway: " +
clasz.getName());
}
val.put(jxent.getKey(), value);
}
return val;
}
This is the bit that I want to solve:
if (clasz.isAssignableFrom(Boolean.class))
{
value = (T)(Boolean.parseBoolean(str));
} else if (clasz.isAssignableFrom(Integer.class))
{
value = (T)(Integer.parseInt(str));
}
I get: Inconvertible types required: T found: Boolean
Also, if possible, I would like to be able to do this with more elegant code, avoiding Class#isAssignableFrom.
Any suggestions?
Sample method invocation:
Map<String, Boolean> foo = fromListOfKeyValuePairs(bar, Boolean.class);
