java - Splitting unknown amount of strings per line

Question

I have a text file structured like this:

    class Object0 extends Object1
    class Object2 extends Object3
    class Object1
    class Object4 extends Object1
    class Object3

I want to split each string and store it. I know how to do this when the number of strings is known on each line, however in this case there can either be two or four words on a given line.

Here's what I have for splitting when the number of strings are known:

public static void main(String[] args) {

        try {
            File f = new File("test.txt");
            Scanner sc = new Scanner(f);
            while(sc.hasNextLine()){
                String line = sc.nextLine();
                String[] details = line.split(" ");
                String classIdentifier = details[0];
                String classNameFirst = details[1];
             // String classExtends = details[2];
             // String classNameSecond = details[3];
            }
        } catch (FileNotFoundException e) {         
            e.printStackTrace();
        }

Use details.length to check if it's 2 or 4.

daniu
– daniu

2017-09-13 06:36:34 +00:00
Commented Sep 13, 2017 at 6:36 — daniu
– daniu, Commented Sep 13, 2017 at 6:36
What's your definition of a working code?

Rey Libutan
– Rey Libutan

2017-09-13 06:37:59 +00:00
Commented Sep 13, 2017 at 6:37 — Rey Libutan
– Rey Libutan, Commented Sep 13, 2017 at 6:37

pleft · Accepted Answer · 2017-09-13 06:42:30Z

1

You can loop on the details array to get each splitted string no matter how many they are. Plus I made some changes in your main method to make it more correct (added a finally clause to close the Scanner resource).

public static void main(String[] args) {

    Scanner sc = null;
    try {
        File f = new File("test.txt");
        sc = new Scanner(f);
        while(sc.hasNextLine()){
            String line = sc.nextLine();
            String[] details = line.split(" ");
            for(String str: details) {
                //variable str contains each value of the string split
                System.out.println(str);
            }
        }
    } catch (FileNotFoundException e) {
        e.printStackTrace();
    } finally {
        sc.close();
    }
}

edited Sep 13, 2017 at 6:42

answered Sep 13, 2017 at 6:37

pleft

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Comments

mrq · Accepted Answer · 2017-09-13 07:20:34Z

On each iteration you can check if there are two more words, this way:

public static void main(String[] args) {

    try {
        File f = new File("test.txt");
        Scanner sc = new Scanner(f);
        while(sc.hasNextLine()){
            String line = sc.nextLine();
            String[] details = line.split(" ");
            String classIdentifier = details[0];
            String classNameFirst = details[1];
            // this can be done because you declared there
            // can be only 2 or 4 words per line
            if (details.length==4) {
                String classExtends = details[2];
                String classNameSecond = details[3];
            }
            // do something useful here with extracted fields (store?)
            // before they get destroyed in the next iteration
        }
    } catch (FileNotFoundException e) {         
        e.printStackTrace();
    }
}

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