answer初始化option为空而不是-1

src/main/java/edu/nju/entities/Answer.java

@@ -42,7 +42,7 @@ public class Answer implements java.io.Serializable{
         this.job_id=job_id;
         this.answers=new ArrayList<>();
         for(int i=0;i<optionNum;i++){
-            answers.add("-1");
+            answers.add("");
         }
     }