如何在Java中将输入文件拆分为单词？

Question

I have to read text from an input file in Java, and first split it into lines and then words. This method used here, to my understanding is to store the words in a list. Can you explain me a bit more how this method works or how can I do it differently? Thank you!

import java.util.Arrays;

public class StoreLinesFormat {
    private ArrayList<ArrayList<String>> storeDataList;

    public StoreLinesFormat() {

    }

    public ArrayList<ArrayList<String>> readFormat(ArrayList<String> inputDataList) {
        ArrayList<String> data = inputDataList;
        if (data != null) {
            storeDataList = new ArrayList<ArrayList<String>>();

            for (String string : data) {
                ArrayList<String> inner = new ArrayList<String>(Arrays.asList(string.split(" ")));
                storeDataList.add(inner);
            }

            return storeDataList;

        } else {
            System.out.println("Array error detected. NULL array value.");
            return null;
        } 
    }

}

Answer 1

Well, let me break it down for you.

public ArrayList<ArrayList<String>> readFormat(ArrayList<String> inputDataList)

This method takes an ArrayList as an argument, the ArrayList used to have a line stored of the file on its every index.

eg 1st Line of file = arrayList(1st index) 2nd Line of file = arrayList(2st index)

So coming down,

for (String string : data) {
                ArrayList<String> inner = new ArrayList<String>(Arrays.asList(string.split(" ")));
                storeDataList.add(inner);
            }

This foreach loops iterate each index and then separates each word with a blank space and creates a new list to store these separated words.

The result is an arrayList having a separate ArrayList on its every index, which have separated words on its every index.

For an alternative - neat solution

In case its too complex for you to handle, take a look at this solution

https://www.javacodex.com/Files/Read-File-Word-By-Word

Answer 2

inputDataList seems to be an ArrayList containing the file line by line.

Then inner gets, for every cycle of that for loop, each word (where "word" means the line separated at the space character, in this case), because split has been called on the single line you're analyzing inside that loop.

At that point the separated words are added en masse to storeDataList , and the cycle repeats for each element of the array (ie each line of the file).