A field which is always assigned before being used from every method that reads it may be better expressed as a local variable. Using a field in such cases gives the impression of mutable state in the class where it isn't necessary.

class Frobnicator {
  private int sum = 0;

  int sum(int a, int b) {
    sum = a + b;
    return sum;
  }

  int sum(int a, int b, int c) {
    sum = a + b + c;
    return sum;
  }

class Frobnicator {
  int sum(int a, int b) {
    int sum = a + b;
    return sum;
  }

  int sum(int a, int b, int c) {
    int sum = a + b + c;
    return sum;
  }

Suppression

This check is suppressed by @SuppressWarnings("FieldCanBeLocal").

It will also be suppressed if the field is annotated with @Keep or an annotation annotated with @Keep.