How to recompile a decompiled .class

[GoatLover]

So basically I wanted to make barricades sturdier and found IsoBarricade.class file, decompiled it, changed health value but can't recompile it back. I just use command prompt and simply call javac *filename* but get errors during compilation. I guess it's because I miss packages/libraries being imported in the .class file? Haven't managed to find answers by googling, so here I am. How to overcome this problem? Thanx.

[Froilen]

I'm also interested in this... 

 

is it posible to mod a zombie behaviors?

 

like make them go directly towards you if you are naked?