CODEWITHSUNDEEP
javadictionaryhashmap
Legofan431
Legofan431

Reputation: 173

value in a Map: Can't parse Integer to Integer

I got a problem even my professor couldn't solve after an hour of investigation: I have a map which stores a highscore value for each level, where the levels are saved as strings and the integer represents the highscore. Now, when I try to read the highscore for a level, I get this very weird problem: Upon calling the method to read the highscore, I get an error saying 

java.lang.String cannot be cast to java.lang.Integer

The code is the following

public Map<String, Integer> highscores = new HashMap<>();
highscores.put("Level1", 35); //Example, we read it from a file
int highscore = highscores.get("Level1");

The error occurs in the third line. Does anyone have an idea why this happens? Integer.parseInt doesn't work either, as that method says it needs a String instead of an Integer as an argument, meaning the right hand side of the line is in fact an Integer. Any help is greatly appreciated.

Upvotes: 1

Views: 2096

Answers (5)

Legofan431
Legofan431

Reputation: 173

I just found the answer in the reading of the file, no idea how I overlooked this one! It said 

highscores = gson.fromJson(new BufferedReader(
                                new FileReader("ressources/highscores.json")),
                    new TypeToken<Map<String, String>>() {}.getType());

Which obviously made the value of the Map a String. Changing the second argument to Map<String, Integer> solves the problem. Thank you for the very fast responses!

Upvotes: 1

Ahsan Qamar
Ahsan Qamar

Reputation: 1

Seems the code that you have mentioned here is perfectly fine, this problem is most likely occurring when you are reading from a file.

Are you sure you are converting whatever you read from the file into an Integer before doing a put() into the Map?

May be you are trying to do something like this:

public class Test {
    public static Map<String, Integer> highscores = new HashMap<>();

    public static void main(String[] args) throws IOException {
        BufferedReader reader = new BufferedReader(new InputStreamReader(Test.class.getResourceAsStream("input.txt")));

        String line = null;
        while ((line = reader.readLine()) != null) {
            String[] tokens = line.split(",");
            highscores.put(tokens[0], Integer.parseInt(tokens[1]));
        }

        System.out.println(highscores.get("Level1"));
        System.out.println(highscores.get("Level2"));
    }
}

Input file

Level1,35
Level2,65

Output

35
65

Upvotes: 0

dabaicai
dabaicai

Reputation: 999

You should determine the element of highscores type.Like following code:

System.out.println(highscores.get("Level1").getClass());

In my guess,the result of above code is not class java.lang.Integer,if the result is Class java.lang.String

you can modify your code to following:

    Map<String, Integer> highscores = new HashMap<>();
    highscores.put("Level1", 35); //Example, we read it from a file
    Object item=highscores.get("Level1");
    if(item.getClass().equals(String.class)) {
        highscore= Integer.parseInt((String) item);
    }else if(item.getClass().equals(Integer.class)){
        highscore=(Integer)item;
    }

Upvotes: 0

Florian S.
Florian S.

Reputation: 446

When you say that you read it from a file, are you sure that it is an Integer and not a String?

The line of code

int highscore = highscores.get("Level1");

does two things and is similar to the following:

Integer highscoreObj = highscores.get("Level1");
int highscore = highscoreObj.intValue();

What happens when you try this one?

Upvotes: 1

sorayadragon
sorayadragon

Reputation: 1087

Sounds like when you're reading the score from a file, it's reading it as a string and then trying to stick it into the HashMap as a String object instead of an Integer object. That's where this exception comes from:

java.lang.String cannot be cast to java.lang.Integer

Upvotes: 1

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