Generics 5 - unexpected type, found: java.lang.Object expected: reference

[milan chudik]

Hi guys,

I have a strange problem with one generics code found in one GWT
library. This compile fine with java 6 but not with java 5.
In fact I can compile it in eclipse with java 5, so this problem appears
only when compiling with maven.

I reproduced this error with this code:

class:
-----------------------------------
public class  DogBean {
   
    transient protected Object bean;
   
    public <X> X getBean()
    {
        return (X) bean;
    }
   
    public void setBean(Object bean)
    {
        this.bean = bean;
    }
   
   

}
--------------------------------
Call to this class (simplified):

----------------------------------
DogBean stack = new DogBean();
       
        stack.setBean("My doggie");
            
        if(stack.getBean() instanceof String)
        {
            System.out.println("GermanShepherd");
        }
--------------------------------

I get this error on: if(stack.getBean() instanceof String)
-------------------------------------
[INFO] Compilation failure
/home/milan/projects/eclipse/workspace2/Generics/src/main/java/main/SomeClass.java:[24,32]
unexpected type
found   : java.lang.Object
required: reference
------------------------------

This is my pom.xml - only one plugin.
pom.xml:
-----------------------------------------------
...
<build>
        <plugins>
            <plugin>
                <groupId>org.apache.maven.plugins</groupId>
                <artifactId>maven-compiler-plugin</artifactId>
                <configuration>
                    <source>1.5</source>
                    <target>1.5</target>
                </configuration>
            </plugin>
           
        </plugins>
    </build>
...
--------------------------------

Maven version:
--------------------------------
Apache Maven 2.2.1 (r801777; 2009-08-06 21:16:01+0200)
-----------------------

maven command used
--------------------------------
mvn clean install
--------------------------------

When I build it with jdk6 I can compile it without problem. But when I
use jdk5 when building, I get that error.
Problem is our build server use runs on jdk5, as some of our customers
do use jre 5.

I can cast this code like this:


if((Object)stack.getBean() instanceof String)

Then it compiles OK both with jdk5 and jdk6. but this is both ugly and dirty

But where is the problem?

I don't get this error under eclipse(neither under jd5 or jdk6) only
when building with maven

Any clues? Just ask for more info.

 

Regards,

Milan Chudík




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