How to get list of words from a list of lines in java?

Question

If I have two lines, how can I split them into a list of two lists of words? I tried the following code:

ArrayList<String> lines = [Hello World, Welcome to StackOverFlow];
List<String> words;
List<List<String>> listOfWords;
for (int i = 0; i < lines.size(); i++) {
            words = Arrays.asList(lines.get(i).split(" "));
            listOfWords = Arrays.asList(words);
        }
System.out.println(listOfWords);

The output of the above code is

[[welcome, to, StackOverFlow]]

Can someone please help me to get the output as follows?

[[Hello, World], [Welcome, to, StackOverFlow]]

question from:https://stackoverflow.com/questions/65866421/how-to-get-list-of-words-from-a-list-of-lines-in-java

Answer 1

On every iteration of your for loop you are overwriting listOfWords by wrapping your latest words array in a new list. So effectively you will always just have your most recent line's list of words as the only item listOfWords.

To fix this modify following below the body of your for statement similar to the following:

  public static void main(String[] args) {
      String[] lines = {"Hello World", "Welcome to StackOverFlow"};
      List<String> words;
      List<List<String>> listOfWords = new ArrayList<List<String>>(); // Must be instantiated or you will get NullPointerException

      for (int i = 0; i < lines.length; i++) {
          words = Arrays.asList(lines[i].split(" "));
          listOfWords.add(words); //Add to `listOfWords` instead of replace with a totally new one
      }

      System.out.println(listOfWords);
  }

Some of the syntax was not correct so I fixed it. In that process I converted lines into an Array. Tested and confirmed output.