java error,

i have problem with java compiler,
can some one tell me more for this error

Compile ERROR:
0/zi.java:5: cannot access java.lang.Class
class file for java.lang.Class not found
public enum Karti {
^
Note: 0/zi.java uses unchecked or unsafe operations.
Note: Recompile with -Xlint:unchecked for details.
1 error