Use try-with-resources or close this "BufferedReader" in a "finally" clause

Question

Been looking for a way to fix this issue. Read all the previous answers but none helped me out. Could it be any error with SonarQube?

public class Br {

    public String loader(String FilePath){

        BufferedReader br;
        String str = null;
        StringBuilder strb = new StringBuilder();
        try {
            br = new BufferedReader(new FileReader(FilePath));
            while ((str = br.readLine()) != null) {
                strb.append(str).append("\n");
            }
        } catch (FileNotFoundException f){
            System.out.println(FilePath+" does not exist");
            return null;
        } catch (IOException e) {
            e.printStackTrace();
        }
        return strb.toString();
    }
}

Answer 1

You are not calling br.close() which means risking a resource leak. In order to reliably close the BufferedReader, you have two options:

using a finally block:

public String loader(String FilePath) {
    // initialize the reader with null
    BufferedReader br = null;
    String str = null;
    StringBuilder strb = new StringBuilder();

    try {
        // really initialize it inside the try block
        br = new BufferedReader(new FileReader(FilePath));
        while ((str = br.readLine()) != null) {
            strb.append(str).append("\n");
        }
    } catch (FileNotFoundException f) {
        System.out.println(FilePath + " does not exist");
        return null;
    } catch (IOException e) {
        e.printStackTrace();
    } finally {
        // this block will be executed in every case, success or caught exception
        if (br != null) {
            // again, a resource is involved, so try-catch another time
            try {
                br.close();
            } catch (IOException e) {
                e.printStackTrace();
            }
        }
    }

    return strb.toString();
}

using a try-with-resources statement:

public String loader(String FilePath) {
    String str = null;
    StringBuilder strb = new StringBuilder();

    // the following line means the try block takes care of closing the resource
    try (BufferedReader br = new BufferedReader(new FileReader(FilePath))) {
        while ((str = br.readLine()) != null) {
            strb.append(str).append("\n");
        }
    } catch (FileNotFoundException f) {
        System.out.println(FilePath + " does not exist");
        return null;
    } catch (IOException e) {
        e.printStackTrace();
    }

    return strb.toString();
}