How to use resources file and memory in try

I wrote a small piece of code to do some pdf encryption with openpdf, and intellij’s sonarlint was complaining about “Resources should be closed” more details here

non compliant

example java code below

public class PasswordProtectedPDF {
    private static final Logger logger = Logger.getLogger(PasswordProtectedPDF.class.getName());
    static final String USER_PASSWORD = "111";
    static final String OWNER_PASSWORD = "111";

    public static void main(String[] args) {
        try {
            File f = new File("1_protected.pdf");
            FileOutputStream out = new FileOutputStream(f);
            File pdfFile = new File("1.pdf");
            PdfReader reader = new PdfReader(pdfFile.getPath());
            PdfStamper stamper = new PdfStamper(reader, out);

            HashMap<String, String> info = new HashMap<>();
            info.put("Producer", "");
            reader.getInfo().forEach((key, value) -> {
                logger.info("Key: " + key + ", Value: " + value);
            });
            stamper.setInfoDictionary(info);
            stamper.setEncryption(USER_PASSWORD.getBytes(), OWNER_PASSWORD.getBytes(), PdfWriter.ALLOW_PRINTING, PdfWriter.ENCRYPTION_AES_128);

            stamper.close();
            logger.info("Password protected PDF created successfully.");
        } catch (IOException e) {
            logger.severe("Error creating password protected PDF: " + e.getMessage());
        }
    }
}

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Compliant

public class PasswordProtectedPDF {
    private static final Logger logger = Logger.getLogger(PasswordProtectedPDF.class.getName());
    static final String USER_PASSWORD = "111";
    static final String OWNER_PASSWORD = "111";

    public static void main(String[] args) {
        try (
                FileOutputStream out = new FileOutputStream(new File("1_protected.pdf"));
                PdfReader reader = new PdfReader(new File("1.pdf").getPath())
        ) {
            PdfStamper stamper = new PdfStamper(reader, out);

            HashMap<String, String> info = new HashMap<>();
            info.put("Producer", "");
            reader.getInfo().forEach((key, value) -> {
                logger.info("Key: " + key + ", Value: " + value);
            });
            stamper.setInfoDictionary(info);
            stamper.setEncryption(USER_PASSWORD.getBytes(), OWNER_PASSWORD.getBytes(), PdfWriter.ALLOW_PRINTING, PdfWriter.ENCRYPTION_AES_128);

            stamper.close();
            logger.info("Password protected PDF created successfully.");
        } catch (IOException e) {
            logger.severe("Error creating password protected PDF: " + e.getMessage());
        }
    }
}

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just a reminder we can define multiple resources in try block

try (
                FileOutputStream out = new FileOutputStream(new File("1_protected.pdf"));
                PdfReader reader = new PdfReader(new File("1.pdf").getPath())
        )

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find full working example here

原文链接：How to use resources file and memory in try