Compilation error with JDK8 and Guava

[Olivier Bourgain]

Hi all,

I tried to compile my project at work with the JDK 8 and I get a
compilation error.

The simplest example which I was able to extract is the following. It uses
Guava 1.14.0.1.

import java.util.LinkedHashMap;
import java.util.List;
import java.util.Map;
import com.google.common.collect.Lists;

public class TestCase {

   public static <K, V> Map<K, V> reverseMap(List<Map.Entry<K, V>> list) {
      return toMap(Lists.reverse(list));
   }

   public static <K, V> Map<K, V> toMap(List<Map.Entry<K, V>> list) {
      Map<K, V> result = new LinkedHashMap<>();
      for (Map.Entry<K, V> entry : list)
         result.put(entry.getKey(), entry.getValue());
      return result;
   }
}

The compilation error is :

» javac -cp lib/guava-14.0.1.jar src/TestCase.java
src/TestCase.java:9: error: method toMap in class TestCase cannot be
applied to given types;
      return toMap(Lists.reverse(list));
             ^
  required: List<Entry<K#1,V#1>>
  found: List<Entry<K#2,V#2>>
  reason: inferred type does not conform to equality constraint(s)
    inferred: Entry<Object,Object>
    equality constraints(s): Entry<Object,Object>,Entry<K#2,V#2>
  where K#1,V#1,K#2,V#2 are type-variables:
    K#1 extends Object declared in method
<K#1,V#1>toMap(List<Entry<K#1,V#1>>)
    V#1 extends Object declared in method
<K#1,V#1>toMap(List<Entry<K#1,V#1>>)
    K#2 extends Object declared in method
<K#2,V#2>reverseMap(List<Entry<K#2,V#2>>)
    V#2 extends Object declared in method
<K#2,V#2>reverseMap(List<Entry<K#2,V#2>>)
1 error


The java version is :

java version "1.8.0-ea"
Java(TM) SE Runtime Environment (build 1.8.0-ea-b82)
Java HotSpot(TM) Server VM (build 25.0-b23, mixed mode)

The same code compiles without error with Java 1.7.


Olivier Bourgain