Java unchecked or unsafe operations message

Question

I am getting the following error when compiling a Java class in BlueJ.

AuctionManager.java uses unchecked or unsafe operations.

This error is only displayed when the following deserialization code is in one of my functions:

try {
  ObjectInputStream in = new ObjectInputStream(new FileInputStream(Filename));
  ArrayList<AuctionItem> AuctionList = (ArrayList<AuctionItem>) in.readObject();
  in.close();
}
catch (Exception e) {
  e.printStackTrace();
}

Can I please have some information as to why this error is being displayed, and some help to use the deserialization code without the error.

score 1 · Answer 1 · answered May 13 '13 at 02:42

1

First the message you get is not an error, is it a warning; it doesn't prevent you program from compiling, or running.

As for the source, it is this line:

ArrayList<AuctionItem> AuctionList = (ArrayList<AuctionItem>) in.readObject();

Since you are casting an object (readObject returns an Object) to a parameterized type (ArrayList<AuctionItem>).

answered May 13 '13 at 02:42

zw324

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What is the best way to fix the code so that the warning does not show? – user2351151 May 13 '13 at 04:55

score 1 · Answer 2 · edited May 23 '17 at 11:57

user2351151: You can do this for warning doesn't show:

ArrayList tempList; // without parameterized type 
try {
  ObjectInputStream in = new ObjectInputStream(new FileInputStream(Filename));
  tempList = (ArrayList) in.readObject();
  for (int i = 0; i < tempList.size(); i++) {
    AuctionList.add(i, (AuctionItem)tempList.get(i)); // explict type conversion from Object to AuctionItem
  }
  in.close();
}
catch (Exception e) {
  e.printStackTrace();
}

You must rewrite ArrayList with explict type conversion (you can use temporary ArrayList without parameterized type).

Java unchecked or unsafe operations message

2 Answers2