Ignore duplicate in string and print string once

Question

Pretty much for my assignment I have to List all the courses (just the course code) that have classes in a given building on a given day such that any part of the class is between the given times. Each course involved should only be listed once, even if it has several classes. I have done everything except listing the course once, even if it has several classes. How do I ignore duplicate strings from a file?

public void potentialDisruptions(String building, String targetDay, int targetStart, int targetEnd){
 UI.printf("\nClasses in %s on %s between %d and %d%n",
 building, targetDay, targetStart, targetEnd);
 UI.println("=================================");
 boolean containsCourse = false;
 try {
 Scanner scan = new Scanner(new File("classdata.txt"));
 while(scan.hasNext()){
 String course = scan.next(); 
 String type= scan.next(); 
 String day = scan.next(); 
 int startTime = scan.nextInt(); 
 int endTime = scan.nextInt(); 
 String room = scan.next();
 if(room.contains(building)){ 
 if(day.contains(targetDay)){
 if(endTime >= targetStart){
 if( startTime<= targetEnd){
 UI.printf("%s%n", course); 
 containsCourse = true;
 }
 }
 } 
 }
 }
 if(!containsCourse){
 UI.println("error");
 }
 }
 catch(IOException e){
 UI.println("File reading failed");
 }
 UI.println("=========================");
}

• Stultuske: Add them all to a collection that doesn't allow duplicates and print all the elements in there.
• singhakash: Use HashSet to avoid duplicates elements
• Nanda Ardianto: can you pls explain? I got an error saying no suitable constructor. Sorry, im new at this. @singhakash

Answer 1

You can put all the string token in Set and check if that token contain in Set befor you process further as below :-

// Declration
.... 
Set courseSet = new HashSet();
...
// Check befor you process further 
if(!courseSet.contains(course))
{
...
// Your Code...
...
courseSet.add(course)
}

• Nanda Ardianto: I have tried to do that, if(!courseSet.contains(course)){ courseSet.add(course); UI.printf("%s%n", course); containsCourse = true; } but it does not work, it still displays duplicates.

Answer 2

You could put the courses in a Set and loop over them since a Set always contains unique values.