如何从Java中的文本文件读取列表

Question

I am trying to read data from a text file which has multiple lines, for example, look the image below, it is my text file

Given a keyword from the user which is the first string in the list from the text file. I want to print the list or line corresponding to the keyword given. For example, if I am giving the keyword=59d2211ec3671594c987d008f89f043e97670a5ba6f08fe073e465116c35b440

Then I want to store [59d2211ec3671594c987d008f89f043e97670a5ba6f08fe073e465116c35b440, id4, id6, id1] as a list.

I have tried using the following function to read the text file and return the data but it's giving me some wrong input.

public static List<String> readLines(File file) throws Exception {
    if (!file.exists()) {
        return new ArrayList<String>();
    }
    BufferedReader reader = new BufferedReader(new FileReader(file));
    List<String> results = new ArrayList<String>();
    String line = reader.readLine();
    while (line != null) {
        results.add(line);
        line = reader.readLine();
    }
    return results;
}

Can someone guide me through on how to implement this in a right way.

Answer 1

if I am giving the keyword

Well, if you're given a value, then you should be using it

readLines(File file, String keyword)

store as a list

Now, I assume you mean split the line into columns. If that's the case, you need to be returning at least a List<List<String>>

However, if not, you can do that later than collecting the lines containing the keyword like so

List<String> results = new ArrayList<String>();
String line = reader.readLine();
while (line != null) {
    if (line.contains(keyword))  results.add(line);
    line = reader.readLine();
}
return results;

FWIW, I would suggest having a look at Java 8 stream functions, including filter , map , and toList