Re: Java type-casting -- Q3
grz01 wrote:
I pasted your code into Eclipse to look at it,
and I *do* get a warning on both return-statements:
Type safety: Unchecked cast from Object to T
That's odd, I'll have to look into that. I didn't notice one.
Try this:
import java.util.HashMap;
import java.util.Map;
/** A type safe heterogeneous container.
*
* @author Brenden
*/
public class HeterogeneousContainer {
Map<String,Class<?>> namesAndTypes;
Map<String,Object> values;
public HeterogeneousContainer( Map<String, Class<?>> namesAndTypes )
{
this.namesAndTypes = new HashMap<String,Class<?>>( namesAndTypes );
values = new HashMap<String,Object>( namesAndTypes.size() );
}
public <T> T get( String name, Class<T> type ) {
if( type == namesAndTypes.get( name ) ) {
return type.cast( values.get( name ) );
}
else {
throw new IllegalArgumentException( "Pair (" + name + ", "+
type+") do not exist." );
}
}
public <T> T put( String name, Class<T> type, T value ) {
if( type == namesAndTypes.get( name ) ) {
return type.cast( values.put( name, value ) );
}
else {
throw new IllegalArgumentException( "Pair (" + name + ", "+
type+") do not exist." );
}
}
public static void main( String[] args )
{
HashMap<String,Class<?>> namesAndTypes = new
HashMap<String,Class<?>>();
namesAndTypes.put( "first", String.class );
namesAndTypes.put( "second", Integer.class );
HeterogeneousContainer test = new HeterogeneousContainer(
namesAndTypes );
test.put( "first", String.class, "A String");
test.put( "second", Integer.class, 4 );
String s = test.get( "first", String.class );
Integer i = test.get( "second", Integer.class );
System.out.println( "Values: " + s + i );
}
}