fix warnings from Refaster

Author: kfriedberger

src/org/sosy_lab/java_smt/example/SimpleUserPropagator.java

@@ -193,11 +193,13 @@ public void onDecision(BooleanFormula expr, boolean value) {
         if (getBackend().propagateNextDecision(disExpr, Optional.of(decisionValue))) {
           // The above call returns "true" if the provided literal is yet undecided, otherwise
           // false.
-          logger.log(
+          logger.logf(
               Level.INFO,
-              String.format(
-                  "User propagator overwrites decision from '%s = %s' to '%s = %s'",
-                  expr, value, disExpr, decisionValue));
+              "User propagator overwrites decision from '%s = %s' to '%s = %s'",
+              expr,
+              value,
+              disExpr,
+              decisionValue);
           break;
         }
       }

src/org/sosy_lab/java_smt/solvers/princess/PrincessAbstractProver.java

@@ -148,7 +148,7 @@ protected void popImpl() {
    * extend the original model.
    */
   Collection<IFormula> getEvaluatedTerms() {
-    return Collections.unmodifiableCollection(evaluatedTerms);
+    return Collections.unmodifiableSet(evaluatedTerms);
   }
 
   /** Track an assignment `term == value` for an evaluated term and its value. */