Build fails with Java 7

I am seeing the following message running IBM Java 7 running branch-1.0 code.
compile:
[echo] contrib: gridmix
[javac] Compiling 31 source files to /home/hadoop/branch-1.0_0427/build/contrib/gridmix/classes
[javac] /home/hadoop/branch-1.0_0427/src/contrib/gridmix/src/java/org/apache/hadoop/mapred/gridmix/Gridmix.java:396: error: type argument ? extends T is not within bounds of type-variable E
[javac] private <T> String getEnumValues(Enum<? extends T>[] e) {
[javac] ^
[javac] where T,E are type-variables:
[javac] T extends Object declared in method <T>getEnumValues(Enum<? extends T>[])
[javac] E extends Enum<E> declared in class Enum
[javac] /home/hadoop/branch-1.0_0427/src/contrib/gridmix/src/java/org/apache/hadoop/mapred/gridmix/Gridmix.java:399: error: type argument ? extends T is not within bounds of type-variable E
[javac] for (Enum<? extends T> v : e) {
[javac] ^
[javac] where T,E are type-variables:
[javac] T extends Object declared in method <T>getEnumValues(Enum<? extends T>[])
[javac] E extends Enum<E> declared in class Enum
[javac] Note: Some input files use unchecked or unsafe operations.
[javac] Note: Recompile with -Xlint:unchecked for details.
[javac] 2 errors

BUILD FAILED
/home/hadoop/branch-1.0_0427/build.xml:703: The following error occurred while executing this line:
/home/hadoop/branch-1.0_0427/src/contrib/build.xml:30: The following error occurred while executing this line:
/home/hadoop/branch-1.0_0427/src/contrib/build-contrib.xml:185: Compile failed; see the compiler error output for details.