Re: Java type-casting -- Q3
On 28 Sep, 03:21, markspace <nos...@nowhere.com> wrote:
grz01 wrote:
Or even better, define a general type like
java.lang.Tuple<T1, ..., Tn>
Type-safe heterogeneous containers: Effective Java, Joshua Bloch. I
just whipped this up, it's untested ('cept for the short static method
at the end).
Note: I've never needed to use one of these either.
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<?>> namesAndT=
ypes )
{
this.namesAndTypes = new HashMap<String,Class<?>>( n=
amesAndTypes );
values = new HashMap<String,Object>( namesAndTypes.s=
ize() );
}
public <T> T get( String name, Class<T> type ) {
if( type == namesAndTypes.get( name ) ) {
return (T) 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 (T) 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 HeterogeneousConta=
iner(
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 );
}
}
Hi Mark,
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