Damage Tool not working?

Hi, I'm trying to do a tool, which can make a coal ore to diamond ore, if rightclicked, and it has 30 uses. The only problem is, when I make the damage item event, I got an error. How can I make it to work?

:clean
:deobfCompileDummyTask
:deobfProvidedDummyTask
:sourceApiJava
:compileApiJava UP-TO-DATE
:processApiResources UP-TO-DATE
:apiClasses UP-TO-DATE
:sourceMainJava
C:\Pylo\MCreator175\forge\build\sources\main\java\mod\mcreator\mcreator_presser.java:80: error: cannot find symbol
:compileJava FAILED
               itemstack.damageItem(1, entity);
               ^
  symbol: variable itemstack
1 error
FAILURE: Build failed with an exception.
* What went wrong:
Execution failed for task ':compileJava'.
> Compilation failed; see the compiler error output for details.
* Try:
Run with --stacktrace option to get the stack trace. Run with --info or --debug option to get more log output.
BUILD FAILED
Total time: 51.297 secs
C:\Pylo\MCreator175\forge>
Task completed with return code 0 in 55397 milliseconds

Sorry for my bad english.