Java: find every unique word in a list and add them to a new list

Question

I'm trying to create a method that finds every unique word in a list and then adds them to a new list. I have tried the following:

   public static void countWords(){
   List<String> list1 = new ArrayList<String>();
   List<String> list2 = new ArrayList<String>();

   String inText = JOptionPane.showInputDialog(null, "Type in text");
   int start = 0;    

     for(int i = 0; i < inText.length(); i++) {
        if(inText.charAt(i) == ' ') {
           list1.add(inText.substring(start,i));
           start = i;
        }                           
     }
        for(int a = 0; a < list1.size(); a++) {
           for(int j = 0; j < a; j++) {
              if(list1.get(a) != list2.get(j)) {
                 list2.add(list2.get(a));                 
              }               
           }           
        }         
}

When I run the program and type in "hi hi hi" I get this error:

Exception in thread "main" java.lang.IndexOutOfBoundsException: Index: 0, Size: 0
at java.util.ArrayList.rangeCheck(ArrayList.java:653)
at java.util.ArrayList.get(ArrayList.java:429)
at RäknaOrd.countWords(RäknaOrd.java:24)
at RäknaOrd.main(RäknaOrd.java:6)

How could I fix this error? Would my approach even work?

Answer 1

Java 8 has a nice stream based method to return a new list with duplicates removed :

List<String> list2 = list1.stream().distinct().collect(Collectors.toList());

Also to split the String and get a List<String> you can avoid a for loop like this :

List<String> list1 = Arrays.asList(inText.split(" "));

But keep in mind that list1 is immutable in this case.

A minimal example for demonstration would be :

String inText = "hi hi hi";
List<String> list1 = Arrays.asList(inText.split(" "));
List<String> list2 = list1.stream().distinct().collect(Collectors.toList());
System.out.println(list2);

Which prints [hi]