Close multiple resources with AutoCloseable (try-with-resources)

Question

I know that the resource you pass with a try, will be closed automatically if the resource has AutoCloseable implemented. So far so good. But what do I do when i have several resources that I want automatically closed. Example with sockets;

try (Socket socket = new Socket()) {     input = new DataInputStream(socket.getInputStream());     output = new DataOutputStream(socket.getOutputStream()); } catch (IOException e) { }  

So I know the socket will be closed properly, because it's passed as a parameter in the try, but how should the input and output be closed properly?

Answer 1

Try with resources can be used with multiple resources by declaring them all in the parenthesis. See the documentation

Relevant code excerpt from the linked documentation:

public static void writeToFileZipFileContents(String zipFileName,                                            String outputFileName)                                            throws java.io.IOException {      java.nio.charset.Charset charset =          java.nio.charset.StandardCharsets.US_ASCII;     java.nio.file.Path outputFilePath =          java.nio.file.Paths.get(outputFileName);      // Open zip file and create output file with      // try-with-resources statement      try (         java.util.zip.ZipFile zf =              new java.util.zip.ZipFile(zipFileName);         java.io.BufferedWriter writer =              java.nio.file.Files.newBufferedWriter(outputFilePath, charset)     ) {         // Enumerate each entry         for (java.util.Enumeration entries =                                 zf.entries();     entries.hasMoreElements();) {             // Get the entry name and write it to the output file             String newLine = System.getProperty("line.separator");             String zipEntryName =                  ((java.util.zip.ZipEntry)entries.nextElement()).getName()               newLine;             writer.write(zipEntryName, 0, zipEntryName.length());         }     } } 

If your objects don't implement AutoClosable (DataInputStream does), or must be declared before the try-with-resources, then the appropriate place to close them is in a finally block, also mentioned in the linked documentation.