Find String or String Array in a File separate them in Java

Question

I have a txt file that includes :

Hello Word
myStrings = [str1, str2, str3]
Goodbye Word

I would like to read the file to find the "myStrings" string then have a loop to check if one of the myStrings value [str1, str2, str3] match with a some variable.

Currently I am finding the myStrings like this:

Scanner scanner = new Scanner(fileName);
while (scanner.hasNextLine()) {
    String fileline = scanner.nextLine();
    String myStringsKey = "myStrings =";
    if(fileline.startsWith(myStringsKey)) { 

    }
}

How can I achieve str2 for instance to check with a defined var? I assume I should use "split".

zappee · Accepted Answer · 2019-09-09 09:49:12Z

1

For parsing your string you can use the following simple method:

public String[] parseMyStrings(String s) {
    int beginIndex = s.indexOf("[") + 1;
    int endIndex = s.indexOf("]");

    s = s.substring(beginIndex, endIndex);

    // split and trim in one shot
    return s.split(("\\s*,\\s*"));
}

Then, your final code can look like this:

Scanner scanner = new Scanner(fileName);
while (scanner.hasNextLine()) {
    String fileline = scanner.nextLine();
    String myStringsKey = "myStrings =";
    if(fileline.startsWith(myStringsKey)) {

        String[] values = parseMyStrings(fileline);
        System.out.println(Arrays.toString(values));

    }
}

I think your code will be more readable and easier to extend or modify if you put the parsing logic into a separate method.

edited Sep 9, 2019 at 9:49

answered Sep 9, 2019 at 9:43

zappee

23.2k15 gold badges97 silver badges157 bronze badges

Sign up to request clarification or add additional context in comments.

Comments

Nicholas K · Accepted Answer · 2019-09-09 09:54:38Z

1

You can make use of a regex and include it within the if block:

if (fileline.startsWith(myStringsKey)) {
    // regex to extract text within brackets
    Pattern p = Pattern.compile("(?<=\\[).+?(?=\\])");  
    Matcher m = p.matcher(fileline);

    while (m.find()) {
        System.out.println(m.group().split(",")[1]); // str2
    }
}

edited Sep 9, 2019 at 9:54

answered Sep 9, 2019 at 9:38

Nicholas K

15.4k8 gold badges35 silver badges59 bronze badges

5 Comments

dicle Over a year ago

but i need to check if a defined var equals str1 or str2 do we have a way to define dynamically instead of sayin [1]?

Mak Over a year ago

What this will return ? With which string it will compare ?Lets say this is a string "myStrings = [[st[r1, str2, str3]" and i want str3 as a output

dicle Over a year ago

I meant for instance i have defined static var myStatic="str3" and i have returned str1, str2, str3 between [ - ] these chars with your way. Comparison ill do between myStatic and the all other 3 strings. if i give [1] as u did ill get only str2 but i wanna find str3 or str1 according to defined one. - and in my project defined var will be dynamic ill get from user for instance.

Nicholas K Over a year ago

You can loop through the array rather than accessing the index directly and then check - is that what you need?

Nicholas K Over a year ago

@Mak: Once the line is split you can loop through it and check. Is that your downvote btw?

Little Santi · Accepted Answer · 2019-09-09 09:29:00Z

0

You have to parse the line's contents: You should first tear out the brackets, and then split the string by commas and add every item to a Set, which will contain the different values.

Then, checking if that set contains your desired value is immediate.

answered Sep 9, 2019 at 9:29

Little Santi

8,8532 gold badges22 silver badges50 bronze badges

Comments

Mak · Accepted Answer · 2019-09-09 09:38:44Z

0

In a very simple way,

 Scanner scanner = new Scanner(fileName);
    while (scanner.hasNextLine()) {
        String fileline = scanner.nextLine();
        String myStringsKey = "myStrings =";
        if(fileline.startsWith(myStringsKey)) { 
            String[] temp = fileline.replaceAll("myStrings =","").replaceAll("\\[", "").replaceAll("\\]", "").trim().split(",");
                for (int i = 0; i < temp.length; i++) {
                    if(temp[i].trim().equalsIgnoreCase("str2")){
                        System.out.println("Str2 matched");
                    }
                }
        }
    }

answered Sep 9, 2019 at 9:38

Mak

1,0768 silver badges20 bronze badges

2 Comments

Nicholas K Over a year ago

This would fail if the strings include a bracket because it will replace the brackets within each string as well. For eg: ["ab[b", "zx[ccc"]

Mak Over a year ago

There are several ways to prevent them to replace such as fileline.replaceFirst("\[", "") or substring excluding first and last char, I just show him the way to do.

Nicholas K · Accepted Answer · 2019-09-25 10:17:00Z

0

scanner = new Scanner(new File(fileName));
while (scanner.hasNextLine()) {
   String fileline = scanner.nextLine();
   if(fileline.contains("myStrings")) {
      String string = fileline.substring(fileline.indexOf("[") + 1, fileline.indexOf("]"));
      String[] vars = string.split(",");
      System.out.println(Arrays.toString(vars));
   }
}

edited Sep 25, 2019 at 10:17

Nicholas K

15.4k8 gold badges35 silver badges59 bronze badges

answered Sep 9, 2019 at 9:59

Prateek Sen

4223 silver badges12 bronze badges

Collectives™ on Stack Overflow

Find String or String Array in a File separate them in Java

5 Answers 5

Comments

5 Comments

Comments

2 Comments

Comments

Your Answer

Hot Network Questions

Collectives™ on Stack Overflow

5 Answers 5

Comments

5 Comments

Comments

2 Comments

Comments

Your Answer

Sign up or log in

Post as a guest

Related