can be final: don't suggest final if field was not initialized (IDEA-167670)

java/java-analysis-impl/src/com/intellij/codeInspection/canBeFinal/CanBeFinalInspection.java

@@ -161,6 +161,7 @@ public class CanBeFinalInspection extends GlobalJavaBatchInspectionTool {
         psiIdentifier = ((PsiMethod)psiMember).getNameIdentifier();
       }
       else if (refElement instanceof RefField) {
+        if (!((RefField)refElement).isUsedForWriting()) return null;
         if (!isReportFields()) return null;
         psiIdentifier = ((PsiField)psiMember).getNameIdentifier();
       }

java/java-tests/testData/inspection/canBeFinal/fieldImplicitWrite/expected.xml

@@ -1,9 +1,2 @@
 <?xml version="1.0" encoding="UTF-8"?>
-<problems>
-  <problem>
-    <file>Test.java</file>
-    <line>3</line>
-    <description>Declaration can have final modifier</description>
-  </problem>
-
-</problems>
+<problems/>