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I have an input file called input.txt with a list of names. I have no problem displaying all the names and putting them in alphabetical order with both display and sort methods. But what I am currently struggling to do is create a method where I can count the recurrence of each name in the file. I would grealty appreciate if anyone could help me with this, and find a way to create this method.

public class Names {

public static void display(ArrayList<String> names) {
    for (int i = 0; i < names.size(); i = i + 1) {
        System.out.println(names.get(i));
    }
}

public static int find(String s, ArrayList<String> a) {
    for (int i = 0; i < a.size(); i = i + 1) {
        String str = a.get(i);
        if (str.equals(s)) {
            return i;
        }
    }
    return -1;

}

public static void capitalize(ArrayList<String> names) {
    for (int i = 0; i < names.size(); i = i + 1) {
        String name = names.get(i);
        if (!name.isEmpty()) {
            String firstLetter = "" + name.charAt(0);
            names.set(i, firstLetter.toUpperCase() + name.substring(1).toLowerCase());

        }
    }
}

public static void sort(ArrayList<String> names) {
    for (int i = 0; i < names.size() - 1; i = i + 1) {
        int Min = i;
        for (int j = i + 1; j < names.size(); j = j + 1) {
            if (names.get(j).compareTo(names.get(Min)) < 0) {
                Min = j;
            }
        }
        String tmp = names.get(i);
        names.set(i, names.get(Min));
        names.set(Min, tmp);

    }

}

public static void getNames(ArrayList<String> fn, ArrayList<String> ln) throws IOException {
    Scanner kb = new Scanner(System.in);
    System.out.println("What is the input flie?");
    String names = kb.next();
    File inpFile = new File(names);
    Scanner in = new Scanner(inpFile);

    while (in.hasNext()) {
        String firstName = in.next();
        String lastName = in.next();
        fn.add(firstName);
        ln.add(lastName);

    }

}

private int countOccurence(String name, ArrayList<String> names){
 int count = 0;
 for(int i =0; i <= names.size; i++){
    if(name.equalsIgnoreCase(names.get(i))){
        count++;
    }
 }
 return count;

}

public static void main(String[] args) throws IOException {

    ArrayList<String> first = new ArrayList<>();
    ArrayList<String> last = new ArrayList<>();
    getNames(first, last);
    capitalize(first);
    capitalize(last);

    ArrayList<String> allNames = new ArrayList<>();
    for (int i = 0; i < first.size(); i++) {
        allNames.add(last.get(i) + ", " + first.get(i));
    }
    System.out.println("*******All Names******");

    sort(allNames);
    display(allNames);

    System.out.println("*****First Name Count***");

    for(int i =0; i <= first.size; i++){
    int count = countOccurence(first.get(i), first);
System.out.println(first.get(i) + " occured " + count + " times.");

}

    System.out.println("****Last Name Count****");

    sort(last);
    display(last);

}

}

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4
  • Do you need a separate count for each name, or will you take input on the name to count? They suggest different solution.. Commented Nov 17, 2015 at 3:02
  • I posted all the methods I have and the main method I have so far Commented Nov 17, 2015 at 3:05
  • I know i have to use the find method or at least I should. But i am confused as to how to change it to count because right now it just gives me the index of where each name first appears in the list Commented Nov 17, 2015 at 3:07
  • I think it would be best to create a method private int countOccurence(String name) which takes a first name or last name as an argument and returns the number of occurences. go through the loop and count them. Commented Nov 17, 2015 at 3:15

2 Answers 2

Reset to default
3

Use Map structure for those case:

Map<String, Integer> recurence = new HashMap<>();
int count;
for (String name : names) {
    if (recurence.containsKey(name)) {
        count = recurence.get(name) + 1;
    } else {
        count = 1;
    }
    recurence.put(name, count);
}
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3 Comments

So with this, would i just use it in the main for every name or as a method that I call everytime in the main? Sorry if this is a stupid question, but i am still a beginning programmer.
yes, with this you can build a data structure like key is the name and value is the recurrence times, so you can get recurrence time by each name on demand
Much better solution, since you only need to iterate over the name once, and inserts are fast. O(n) for iteration, and O(1) for put/get
1

create a method that counts the occurences:

public static int countOccurence(String name, ArrayList<String> names){
     int count = 0;
     for(int i =0; i <= names.size(); i++){
        if(name.equalsIgnoreCase(names.get(i))){
            count++;
        }
     }
     return count;
}

To use it, go through the loop in you Main ( or you can create another method)

for(int i =0; i <= first.size; i++){
    int count = countOccurence(first.get(i), first);
    System.out.println(first.get(i) + " occured " + count + " times.");
}
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6 Comments

I created the method and tried to put what you have for me in the main method, but it keeps giving me an error in the main method saying that i have to create a method countOccurence even though i already have one. Do you know why I may be having this problem?
From the method you gave me I have to create a string and then the array list based on the parameters, but what would i put in the string I create?
sorry, I forgot to include the Arraylist to the method call. countOccurence(first.get(i), first); edited.
On a side note, you should rename your Arraylist into something that tells you that it's a list e.g. firstNames tells you that it's a list of first names.
I updated the code using what you have given but the program won't run. In the method it gives an error in the for loop saying " size has private access in ArrayList". Then in the main method at the function call it gives another error saying " non static method cannot be referenced from a static context". Do you know what I could to do to get it running?
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