try中如何使用资源文件和内存

我编写了一小段代码来使用 openpdf 进行一些 pdf 加密，而 intellij 的 sonarlint 抱怨“资源应该关闭”更多详细信息请参见这里

不合规

下面的示例 java 代码

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 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());
        }
    }
}

合规

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 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());
        }
    }
}

只是提醒我们可以在 try 块中定义多个资源

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

在这里找到完整的工作示例