You have a ton of problems with syntax but that aside your logic problems stems from messy seperation of what each loop does.
Outer loop: adds 2 to the term, adds the fac result to the output sum.
Inner loop: Fac'ing the term.
Im not sure you are fac'ing right. Try using recursion as it brings beautiful solution to fac'ing.
public void myFunc(int n){ int sum = 0; int term = 2; for (int i = 1; i <= n ; i++){ if(i % 2 == 0) { sum -= myFac(term); } else { sum += myFac(term); } term += 2; } System.out.println(sum); } Remember to use highlight tags, or you code is unreadable