when I operated the step 5. "sudo ln -sf /System/Library/Frameworks/JavaVM.framework/Commands/javaws /usr/bin/javaws", a message returned says: "Operation not permitted"

when I operated the step 5. "sudo ln -sf /System/Library/Frameworks/JavaVM.framework/Commands/javaws /usr/bin/javaws", a message returned says: "Operation not permitted", would you please help with it?

the purpose of mine to do this is to roll back my java to 6, from a newer version.