Keep getting this error when compiling using Maven:
type parameters of <X>X cannot be determined; no unique maximal instance exists for type variable X with upper bounds int,java.lang.Object
Generics type interference cannot be applied to primitive types. But I thought since Java5, boxing/unboxing mechanism works seamlessly between primitive types and wrapper classes.
In any case, the strange thing is Eclipse doesn't report any errors and happily compiles. I'm using JDK1.6.0_12. What could possibly be the problem here?
This issue can occur when your code is generic and it calls another method that has a generic return type. Sometimes the compiler gets confused trying to figure out how to resolve the method call / return type.
It can be resolved by adding an explicit cast to your code.
// Old code:
public T getValue() {
return otherMethod(); // otherMethod has the signature: <RT> RT otherMethod() { ... }
}
// New code:
@SuppressWarnings("unchecked")
public T getValue() {
return (T) otherMethod(); // the cast tells the compiler what to do.
}
I met the same error,use ant.
Because when compile by ant or maven,javac use JDK to compile.But in eclipse,it has JDT,that can compile success.
I add below script in my build.xml file:
<property name="build.compiler" value="org.eclipse.jdt.core.JDTCompilerAdapter" />
Then,ant can build success.
I am not familiar with Maven. Maybe,it can set the compiler?
In my source code,there are many code like this:
public <X> X find(String hql, Object... values)
{
return (X) HibernateUtils.createQuery(getSession(), hql, values).uniqueResult();
}
Maybe your code too.
But,use JDT,the success is't the final success,in ant.
build.xml can build success only in eclipse.
when I run ant from windows command,fail. Throw another error:
Class not found: org.eclipse.jdt.core.JDTCompilerAdapter
PS, I have copy jar files about JDT in eclipse plugin to ant_home/lib directory.
Wish a little help to you.And our problem can solve.
It definitely has to do something with the JDK versions maven and eclipse are using. Also make sure your Compiler compliance level in eclipse points to the right JDK version.
