Question

I am new to java so please go easy on me. I have a hashmap which contains String keys and Boolean values like the following.

Map<String, Boolean> states = new HashMap<String, Boolean>();
states.put("b_StorageAvailable", true);
states.put("b_StorageWritable", true);

Which I am returning from a function. Once I get this somewhere else, I would like to be able to call an if statement on one of these to see if its true or false.

if(states.get("b_StorageAvailable")) { 
    //Do this 
}

But java keeps showing me that I need this to be a Boolean type, and it is a Map type. How can I do this easily?

UPDATE

It should be noted that the code I am calling the function with and getting the return value looks like this,

Map states = this.getExternalStorageStatus();

Answer 1

Your code looks fine. Just make sure you’re using exactly the same key ("b_StorageAvailable"). Because the Boolean in the Map is auto-boxed to a primitive boolean, if there is no entry in the Map for the supplied key, you’ll get a NullPointerException.

I would also check that your function’s return type and the local variable are defined as HashMap<String, Boolean> as well. If it is untyped, then you won’t be able to assume it’s a Boolean in the Map.

public static void main(String[] args) {

    Map<String, Boolean> states = new HashMap<String, Boolean>();
    states.put("b_StorageAvailable", true);
    states.put("b_StorageWritable", true);

    if(states.get("b_StorageAvailable")){ // works fine!
        System.out.println("storage is available!");
    }

    Map states2 = new HashMap<String, Boolean>(); // untyped!
    states.put("b_StorageAvailable", true);
    states.put("b_StorageWritable", true);
    if(states2.get("b_StorageAvailable")){ // Type mismatch: cannot convert from Object to boolean
        System.out.println("storage is available!");
    }

}

So all you need to do is change

Map states = this.getExternalStorageStatus(); 

to

Map<String, Boolean> states = this.getExternalStorageStatus();

And potentialy change the return type of getExternalStorageStatus()

private Map<String,Boolean> getExternalStorageStatus(){
 ...
}