[java] [student_grades] Extract method (guard clause)

Author: JavierCane

examples/java/java-student_grades-03_if_guard_clause/src/main/java/tv/codely/student_grades/StudentGradeCalculator.java

@@ -38,13 +38,7 @@ public float calculateGrades(final List<Pair<Integer, Float>> examsGrades, final
             return 0f;
         }
 
-        int gradesWeightSum = gradesWeightSum(examsGrades);
-
-        if (gradesWeightSum > 100) {
-            throw new GradesWeightOverMaxException();
-        } else if (gradesWeightSum < 100) {
-            throw new GradesWeightBelowMinException();
-        }
+        ensureGradesWeightSumIs100percent(examsGrades);
 
         float gradesSum = gradesSum(examsGrades);
 
@@ -55,6 +49,16 @@ public float calculateGrades(final List<Pair<Integer, Float>> examsGrades, final
         return gradesSum;
     }
 
+    private void ensureGradesWeightSumIs100percent(List<Pair<Integer, Float>> examsGrades) {
+        int gradesWeightSum = gradesWeightSum(examsGrades);
+
+        if (gradesWeightSum > 100) {
+            throw new GradesWeightOverMaxException();
+        } else if (gradesWeightSum < 100) {
+            throw new GradesWeightBelowMinException();
+        }
+    }
+
     private float gradesSum(List<Pair<Integer, Float>> examsGrades) {
         float gradesSum = 0f;
         for (Pair<Integer, Float> examGrade : examsGrades) {