Reading file and adding it to an array through a method

I am creating an Array List of zip codes (29000 of them) and I am having trouble getting it to add the complete zipcodes to the arrayList. I think my problem is actually using the ArrayList because it is instantiated in another method.

Code Java:

---

 
public class ZipCodeDatabase {
 
 private ArrayList <ZipCode> list;
 
    public ZipCodeDatabase() {
        list = new ArrayList<ZipCode>();
    }
 
    public void readZipCodeData (String filename) throws IOException {
        String info;
        Scanner fileReader;
        Scanner lineReader;
 
        fileReader = new Scanner(new File(filename));
 
        while(fileReader.hasNext()) {
            info = fileReader.nextLine();
 
            lineReader = new Scanner(info);
            lineReader.useDelimiter(",");
 
            int zip = lineReader.nextInt();
            String city = lineReader.next();
            String state = lineReader.next();
            double longtitude = lineReader.nextDouble();
            double latitude = lineReader.nextDouble();
 
            ZipCode z = new ZipCode(zip, city, state, latitude, longtitude);
            list.add(z);
        }
}

---

This uses the ZipCode method which is in another class and has the code

Code Java:

---

  public ZipCode (int pZip , String pCity , String pState , double pLat , double pLon) {
        zipcode = pZip;
        city = pCity; 
        state = pState;
        latitude = pLat;
        longitude = pLon;
 
 
    }

---

The class and method names are all given in the project. I'm a beginner Java student and this is my first time posting on these forums so don't hurt me too badly =P

Thanks,
PeskyToaster

So what is your problem? Do you get error messages? If so you will need to post them since we don't read minds.

Try using the hasNextLine() method of the Scanner class instead of hasNext, see if that makes any difference.
Unless you explicitly say what's supposed to happen, and what IS happening, we would mainly just need to guess.

It would be better if you gave more information, i.e. is it only 5 tokens per line in your text file? etc

I'm am testing out a method called

Code Java:

---

 
 public ZipCode findZip (int zip) {
        ZipCode p = new ZipCode(0);
        for(int i = 0; i < list.size(); i++) {
            if (list.get(i).getZip() == zip) {
                return list.get(i);
            }
            else {
                return null;
            }
        }
        return p;
    }

---

It should return the entire Zipcode of the text file, for example the first entry of the file is

99501,ANCHORAGE,AK,61.223145,-149.852843

So if I input 99501 it should return a toString method of the information which is

Code Java:

---

public String toString() {
        address = city + ", " + state + " " + zipcode;
        return address;
    }

---

I forgot that the toString is supposed to be in the findZip method as well to format what it returns.

If I input 99501 I should get ANCHORAGE, AK 99501.
What I am getting is null.

I'm also getting a compiler warning of "C:\Users\***\ZipCodeDataBase.java uses unchecked or unsafe operations.
Recompoile with /XIint:unchecked for details."

I hope that is enough information

Take a look at your if statement. You compare the first ZipCode object to the zipcode you are searching for and if it matches you return the ZipCode object else you return null. Which means your find method will only work if the zipcode you are looking for is the first in the list.

Why is it only comparing to the first one?

Because that is all you code does.

Grab the first object in the list
Do a comparison
If it matches return object
Else return null

It never goes around the loop a second time to compare the second, third etc object in the list. To see what I mean add this line before the if statement:

Code java:

---

System.out.println("Loop #" + i);

---

You will see that it will only ever print out one line regardless of which zipcode you search for.

What do I need to do to fix this? I thought the i++ would send it through the for loop until it reaches list.size().



EDIT: By removing the null I can get it to search through the list and find what I need but according to the project I need a null if the zip code input is not found. I also changed the for loop to a while so it looks like this now

Code Java:

---

 public ZipCode findZip (int zip) {
        ZipCode p = new ZipCode(0);
       int i = 0;
       while (i < list.size()) {
 
            if (list.get(i).getZip() == zip) {
                return list.get(i);
            }
           /* else {
                return null;
            }*/
            i++;
        }
        return p;
    }

---

So it isn't returning null. What is it returning instead?

When I commented out the null it worked correctly and found the right zip code. But I need to return null if the (int zip) that is inputted is not on the list of zip codes or isn't a valid response.



EDIT: Figured out the null, I just took it out of the for loop. But I have another problem. For this method I need to search for parts of the city and state that match the give string str. So an str of "al" would return zip codes in all states that start with "al" and all cities that start with "al"
When I input my string to test it out I get two bracket [ ] so I am assuming it is not correctly adding the matching zip codes to the ArrayList

Code Java:

---

 public ArrayList search(String str) {
        ArrayList place = new ArrayList(0);
        ArrayList<ZipCode> searchList = new ArrayList<ZipCode>();
        int i = 0;
        while (i < list.size()) {
            str.toUpperCase();
            if ((list.get(i).getCity().substring(0 , str.length()) == str) || (list.get(i).getState().substring(0 , str.length()) == str)) {
                searchList.add(list.get(i));
 
            }
            /*else {
            return null;
            }*/
            i++;  
            return searchList;
        }
        return place;
    }

---

Once again what does it return when it doesn't find the zipcode?

It only returns two empty brackets []. I am just assuming that it is correctly finding the values and something is wrong with adding it into the searchList

Quote:

---

Originally Posted by PeskyToaster

It only returns two empty brackets [].

---

That makes no sense. In no way can your program return brackets. Look at your code very carefully. Inside the loop you search for the zipcode and if you find it that zipcode is returned. If it doesn't find it and the loop ends what happens?

This code is supposed to search through the list of zip codes by city or state and add the ones that match to an arraylist then return that arraylist. So if I type in "new" it should return NEWARK zip codes and NEW YORK etc. Here's is my main method for testing this

Code Java:

---

public class Driver
{
   public static void main(String[] args) throws IOException{
       ZipCodeDatabase t = new ZipCodeDatabase();
 
       t.readZipCodeData("zipcodes.txt");
 
       System.out.println (t.search("al"));
       System.out.println (t.search("chicago"));

---

The output for "al" gives

[]

The output for "chicago" gives the error

java.lang.StringIndexOutOfBoundsException: String index out of range: 7
at java.lang.String.substring(String.java:1955)
at ZipCodeDatabase.search(ZipCodeDatabase.java:67)
at Driver.main(Driver.java:22)


All copied directly from the BlueJ Terminal Window

It is not returning the brackets. What your code does now is return an empty ArrayList and if you try to print an empty List that is the output you see. Why does your method now return an ArrayList when the objective is to find a ZipCode object?

This is a different method from the first question. I posted the new method I needed help on, on the first page. It seems it is not adding the found Zip Codes to the array list

Google "compare strings java"

I now have

Code Java:

---

 
 public ArrayList search(String str) {
 
        ArrayList<ZipCode> searchList = new ArrayList<ZipCode>();
        int i = 0;
        while (i < list.size()) {
            str.toUpperCase();
            if ((list.get(i).getCity().substring(0 , str.length()).equals(str)) || (list.get(i).getState().substring(0 , str.length()).equals(str))) {
                searchList.add(list.get(i));
 
            } 
            return searchList;
        }
        return null;
    }

---

And it still gives the same output

You know have a similar issue as you had before. Pretend you are the computer executing the code line by line. Tell me what happens after the code looks at the first element in the list. Of once again add the line of code about printing the number of times around the loop I suggested earlier.

I see that it skips right to null but I need to have it there somewhere. I know that I was missing an i++ to keep it going along the while loop. What should I return at the end and where in the loop?

Code Java:

---

 
public ArrayList search(String str) {
 
        ArrayList<ZipCode> searchList = new ArrayList<ZipCode>();
        int i = 0;
        while (i < list.size()) {
            str.toUpperCase();
            if ((list.get(i).getCity().substring(0 , str.length()).equals(str)) || (list.get(i).getState().substring(0 , str.length()).equals(str))) {
                searchList.add(list.get(i));
 
 
            } 
            //return searchList;
 
            i++;
            return searchList;
        }
 
    }

---

I'm getting a compile error because it is missing a return statement at the end.

I got the above to work but it prints it out all on one line which I can fix. I have a distance method to find the distance between to inputted zip codes

Code Java:

---

 
 public int distance (int zip1 , int zip2) {
        final double EARTH_RADIUS = 3959;
        int distance;
        double p1 , p2 , p3;
 
        ZipCode z1 = findZip(zip1);
        ZipCode z2 = findZip(zip2);
 
        double lat1 = Math.toRadians((z1.getLatitude()));
        double lat2 = Math.toRadians((z2.getLatitude()));
        double long1 = Math.toRadians((z1.getLongitude()));
        double long2 = Math.toRadians((z2.getLongitude()));
 
        p1 = (Math.cos(lat1)) * (Math.cos(long1)) * (Math.cos(lat2)) * (Math.cos(long2));
        p2 = (Math.cos(lat1)) * (Math.sin(long1)) * (Math.cos(lat2)) * (Math.sin(long2));
        p3 = (Math.sin(lat1)) * (Math.sin(lat2));
 
        distance = (int)((Math.acos(p1 + p2 + p3)) * (EARTH_RADIUS));
 
        return distance;
 
    }

---

The math is off though because if I input 49401 and 90001 the output should be 1841 miles but my output is 2229. I also need to have an if that doesn't accept null values for the entered zips (if zip1 is not on the list) and I have no idea how to do that.