Question

I am getting this error with the following code:

The method getItemProperty(capture#2-of ? extends GenericTest.Item) in the type GenericTest.BaseContainer<capture#2-of ? extends GenericTest.Item> is not applicable for the arguments (GenericTest.Item)

import org.junit.Test;

public class GenericTest {

public class Item {
    private String value;

    public String getValue() {
        return value;
    }

    public void setValue(String value) {
        this.value = value;
    }
}

public class WordItem extends Item {

}

public abstract class BaseContainer<T extends Item> {
    public String getItemProperty(T item) {
        return item.getValue();
    }
}

public class Document extends BaseContainer<WordItem> {
}

public static class ContainerFactory {
  public static BaseContainer<? extends Item> getContainer(Item item) {
     return new GenericTest().new Document();
  }
}

@Test
public void theTest(){
    Item item = new WordItem();
    BaseContainer<? extends Item> container = ContainerFactory.getContainer(item);
    String str = container.getItemProperty(item); //this line does not compile
}
}

I´m using Eclipse Helios with jdk 1.6.0_16.

Answer 1

To get rid of the error, change your code to:

public static class ContainerFactory {
  public static <T extends Item>BaseContainer<T> getContainer(Item item) {
     return (BaseContainer<T>) new GenericTest().new Document();
  }
}

@Test
public void theTest(){
    Item item = new WordItem();
    BaseContainer<Item> container = ContainerFactory.getContainer(item);
    String str = container.getItemProperty(item);
}