does ANT1.6.2 support SUN JDK1.5?

I used Ant1.6.2 and it said that:”
[javac] C:\HibTest\firstHib\src\Test.java:6: cannot access java.lang.Object
[javac] bad class file: C:\Program Files\Java\jdk1.5.0_01\jre\lib\rt.jar(jav
a/lang/Object.class)
[javac] class file has wrong version 49.0, should be 47.0″
How can it be? Help me!