Question

I currently have a compilation issue with Gradle using target 1.7 and source 1.7 vs Eclipse Juno using the built-in 1.7 jdk.

I have 5 classes :

Info.java –> Interface that has no methods (for example)

public interface Info { //... }

RealInfo.java –> Interface that extends the Info interface

public interface RealInfo extends Info { //... }

AbstractManager.java –> Abstract class that has the method “getInfo()“

public abstract class AbstractManager<I extends Info>
{
    public I info;
    public I getInfo()
    {
        return this.info;
    }
}

Manager.java –> Interface that has the method “getInfo()“

public interface Manager
{
    public <I extends Info> I getInfo();
}

DefaultManager.java –> Extends AbstractManager

public class DefaultManager extends AbstractManager<RealInfo> implements Manager
{
    //...
}

If you copy/paste this code into eclipse, everything works fine. There’s no compilation error. However, if I build it with Gradle, using target jdk 1.7, the compiler will not like it :

DefaultManager.java:16: error: DefaultManager is not abstract and does not override abstract method <I>getInfo() in Manager
public class DefaultManager extends AbstractManager<RealInfo> implements Manager
                                                       ^
  where I is a type-variable:
    I extends Info declared in method <I>getInfo()

Do you have any idea on what could happen there?

Answer 1

I’ve found what Javac doesn’t seem to like.

I modified my AbstractManager class to :

public abstract class AbstractManager<I extends Info>
{
    public I info;
    public <I extends Info> I getInfo()
    {
        return (I) this.info;
    }
}

Gradle now accepts this code while compiling with Javac. It’s strange though that it cannot properly infer I to <I extends Info>. Eclipse’s compiler can handle the two syntaxes.