Moving to OT > Soft Dev
Mohit,
These all sound like build path problems.
1) Enum is from Java 5, make sure you are biulding your project with Java5 compiler settings and your build path is using the Java5 libraries and not Java 1.4.
2) You need to fix this first. What you probably did is copy this project from another computer that either had a different JDK installer or had it installed in a different location, so when you loaded it on this machine you have now, it cannot resolve the JRE. You need to fix this by going to the Window > Prefs > Java > Installed JREs preference panel, then going back to your Project Properties, under Java Build Path and Libraries tab. Remove the broken JRE libraries and add the working ones for Java 5.
3) Probably related to #2.