Consider this program using http://hg.netbeans.org/binaries/50986B7D247AF02C3DC25CB26B5FC7D5CF1340E6-ini4j-0.4.1.jar as a library:

---%<---
import org.ini4j.Ini;
public class Demo {
    public Demo() {
        Ini.Section s = new Ini().get("section");
    }
}
---%<---

JDK 6's javac accepts this but JDK 7 rejects it with:

Demo.java:4: incompatible types
        Ini.Section s = new Ini().get("section");
  required: Ini.Section
  found: Object

javap for the library reports:

public class org.ini4j.Ini extends org.ini4j.MultiMapImpl<java.lang.String, org.ini4j.Ini$Section> {
  // nothing more of interest...
}
public class org.ini4j.MultiMapImpl<K extends java.lang.Object, V extends java.lang.Object> extends java.lang.Object implements org.ini4j.MultiMap<K, V> {
  // ...
  public V get(java/lang/Object);
  public V get(java/lang/Object, int);
  // ...
}
public interface org.ini4j.MultiMap<K extends java.lang.Object, V extends java.lang.Object> extends java.lang.Object implements java.util.Map<K, V> {
  // ...
  public abstract V get(java/lang/Object, int);
  // ...
}

Since Ini is a MultiMapImpl<String,Ini.Section>, get(Object) on it should return Ini.Section.

Ini.Section.get(String) is similarly affected; should return String but JDK 7 javac considers it to return Object.