Re: Generics warning message.

On Dec 30, 12:25 pm, Roedy Green <see_webs...@xxxxxxxxxxxxxxxxxxxx>
wrote:
Is there a way to get rid of this warning message?

E:\com\mindprod\vercheck\VerCheck.java:575: warning: [unchecked]
unchecked cast
found : java.lang.Object
required: java.util.ArrayList<com.mindprod.vercheck.AppToWatch>
allRows = (ArrayList<AppToWatch>) ois.readObject();

the code is

ArrayList<AppToWatch> allRows = new ArrayList<AppToWatch>(30);
...
allRows = (ArrayList<AppToWatch>) ois.readObject();
--
Roedy Green Canadian Mind Products
The Java Glossaryhttp://mindprod.com
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There might be a way. I think the following code performs a similar
function to what you are trying to achieve. The code compiles without
warnings or errors and it runs correctly. Nonetheless, it leaves
something to be desired.

import java . io . * ;
import java . util . * ;

class test
{
public static void main ( String [ ] args ) throws Exception
{
ObjectInputStream ois = setupExample ( args ) ;
runExample ( ois ) ;
}

/**
* This just sets up the example.
* It returns an appropriate ObjectInputStream
* (i.e. one that has been stuffed with an ArrayList.
**/
private static ObjectInputStream setupExample ( String [ ] args )
throws Exception
{
ArrayList < String > list = new ArrayList < String > ( ) ;
for ( int i = 0 ; i < args . length ; i ++ )
{
list . add ( args [ i ] ) ;
}
ByteArrayOutputStream bos = new ByteArrayOutputStream ( ) ;
ObjectOutputStream oos = new ObjectOutputStream ( bos ) ;
oos . writeObject ( list ) ;
oos . close ( ) ;
bos . close ( ) ;
byte [ ] b = bos . toByteArray ( ) ;
ByteArrayInputStream bis = new ByteArrayInputStream ( b ) ;
ObjectInputStream ois = new ObjectInputStream ( bis ) ;
return ( ois ) ;
}

/**
* This is the example.
* We think that there is an ArrayList<java.lang.String> in
* the InputStream.
* How to cast it out without throwing warnings?
**/
private static void runExample ( ObjectInputStream ois ) throws
Exception
{
Object object = ois . readObject ( ) ;
ArrayList list1 = ( ArrayList ) ( object ) ;
ArrayList < String > list2 = nowarningCast ( String . class ,
list1 ) ;
for ( String string : list2 )
{
System . out . println ( string ) ;
}
}

/**
* This is how I cast the ArrayList to
* an ArrayList<java.lang.String> without
* casting warnings.
*
* Take heed that this is not safe.
**/
private static < R > ArrayList < R > nowarningCast
( Class < R > clazz , ArrayList in )
{
ArrayList < R > out = new ArrayList < R > ( ) ;
for ( Object val : in )
{
R r = clazz . cast ( val ) ;
out . add ( r ) ;
}
return ( out ) ;
}
}

Emory Merryman
External Concepts Guild
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.

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