javac gives no type safety warning ?

[David Bala�ic]

Hi!

page 578 of the Study Guide says, that when calling a legacy method that add to a Collection, the compiler should give this warning:

javac TestBadLegacy.java
Note: TestBadLegacy.java uses unchecked or unsafe operations.
Note: Recompile with -Xlint:unchecked for details.


I do not get this note/warning !? Neither in Eclipse or when running javac from command line (see below for details).

Content of file TestBadLegacy.java (mostly copied from book):

package stein.generics.mix1;
 
import java.util.*;
import other.Inserter;
 
public class TestBadLegacy {
public static void main(String[] args) {
List<Integer> myList = new ArrayList<Integer>();
myList.add(4);
myList.add(6);
Inserter in = new Inserter();
in.insert(myList); // pass List<Integer> to legacy code
}
}
 

Content of file Inserter.java (mostly copied from book):

package other;
 
 
import java.util.List;
 
public class Inserter {
// method with a non-generic List argument
public void insert(List list) {
list.add(new String("42")); // adds to the incoming list
}
}
 

Commands used:
> javac -source 1.4 -target 1.4 other\Inserter.java
> javac -source 1.5 -target 1.5 -Xlint:unchecked stein\generics\mix1\TestBadLegacy.java

No warnings, with or without -Xlint:unchecked
JDK version is "1.5.0_15" in WinXP 32 bit.

java version "1.5.0_15"
Java(TM) 2 Runtime Environment, Standard Edition (build 1.5.0_15-b04)
Java HotSpot(TM) Client VM (build 1.5.0_15-b04, mixed mode, sharing)

Am I doing something wrong ? (it _was_ late at night...)

Regards,
David

PS: About my account, it is a temporary one, because my real one is stuck in the process of registration. I contacted the admins. Please no discussion of it in _this_ thread. Thanks.
[ May 15, 2008: Message edited by: Slowly Annoyed ]

[Ben Souther]

"Slowly Annoyed ",
Please check your private messages regarding an important administrative matter.
-Ben

[Deepak Bala]

I got the following message in eclipse for this code

      ArrayList check = new ArrayList();
    check.add(new String());  

Type safety: The method add(Object) belongs to the raw type ArrayList. References to generic
type ArrayList<E> should be parameterized

Click on the project on the java perspective and press ctrl + enter. Make sure the java compiler settings point to java 5. Also ensure that you dont get compiler errors when you use generics. Perhaps you have warnings turned off somewhere ?

[Stevi Deter]

Originally posted by Slowly Annoyed:

Commands used:
> javac -source 1.4 -target 1.4 other\Inserter.java
> javac -source 1.5 -target 1.5 -Xlint:unchecked stein\generics\mix1\TestBadLegacy.java

The unchecked warning occurs in the code in Inserter.java when compiled in Java 5 or greater.

By compiling it with the source/target 1.4, you're compiling it in a Java version that knows nothing of Generics, thus no unchecked warnings.

Go ahead and compile all your code with 1.5 (and you don't need the source/target switches if that's your compiler version) and the -Xlint flag.

[David Bala�ic]

Ah, thanks.

So if I write new (generic) code and use a method (that takes a List and adds element to) it from my old non-generic (already compiled) code, the there will be no warning ?

Regards,
David

[Ben Souther]

"Slowly Annoyed ",
Please check your private messages again.
-Ben