Question

Im working on the question below and am quite close but in line 19 and 32 I get the following error and cant figure it out.

foreach not applicable to expression type
for (String place: s)

Question:

Tax inspectors have available to them two text files, called unemployed.txt and taxpayers.txt, respectively. Each file contains a collection of names, one name per line. The inspectors regard anyone who occurs in both files as a dodgy character. Write a program which prints the names of the dodgy characters. Make good use of Java’s support for sets.

My code:

class Dodgy {

public static void main(String[] args) {

    HashSet<String> hs = new HashSet<String>();

    Scanner sc1 = null;
try {sc1 = new Scanner(new File("taxpayers.txt"));} 
        catch(FileNotFoundException e){};
while (sc1.hasNextLine()) {
    String line = sc1.nextLine();
    String s = line;
    for (String place: s) {
        if((hs.contains(place))==true){
            System.out.println(place + " is a dodgy character.");
    hs.add(place);}
    }   
}

    Scanner sc2 = null;
try {sc2 = new Scanner(new File("unemployed.txt"));} 
        catch(FileNotFoundException e){};
while (sc2.hasNextLine()) {
    String line = sc2.nextLine();
    String s = line;
    for (String place: s) {
        if((hs.contains(place))==true){
            System.out.println(place + " is a dodgy character.");
    hs.add(place);}
}
}
}
}

Answer 1

You’re trying to iterate over “each string within a string” – what does that even mean?

It feels like you only need to iterate over each line in each file… you don’t need to iterate within a line.

Secondly – in your first loop, you’re only looking at the first file, so how could you possibly detect dodgy characters?

I would consider abstracting the problem to:

• Write a method to read a file and populate a hash set.
• Call that method twice to create two sets, then find the intersection.