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 severa

Answer 1

In addition to the above answers, This is the improvement added in Java 9.

Java 9 try-with-resources makes an improved way of writing code. Now you can declare the variable outside the try block and use them inside try block directly.because of this you will get following benefits.

• The Resources which it declared outside try( which is effectively final or final) can be automatically close by automatic resource management by just adding them in the try block.
  • You no need to re-refer objects declared outside try block nor need to close them manually as we need to do in Java 7.
  • It also helps to write clean code.

try-with-resource can we write like this in Java 9.

public void loadDataFromDB() throws SQLException {
Connection dbCon = DriverManager.getConnection("url", "user", "password");
try (dbCon; ResultSet rs = dbCon.createStatement().executeQuery("select * from emp")) {
    while (rs.next()) {
        System.out.println("In loadDataFromDB() =====>>>>>>>>>>>> " + rs.getString(1));
    }
} catch (SQLException e) {
    System.out.println("Exception occurs while reading the data from DB ->" + e.getMessage());
}

}

Here automatic resource management will automatically close both the objects dbCon & rs.

For the better understanding of the list of above define use cases please find some Java 7 code.

Example 1:

public void loadDataFromDB() throws SQLException {
Connection dbCon = DriverManager.getConnection("url", "user", "password");
try (ResultSet rs = dbCon.createStatement().executeQuery("select * from emp")) {
    while (rs.next()) {
        System.out.println("In loadDataFromDB() =====>>>>>>>>>>>> " + rs.getString(1));
    }
} catch (SQLException e) {
    System.out.println("Exception occurs while reading the data from DB ->" + e.getMessage());
} finally {
    if (null != dbCon)
        dbCon.close();
}

}

Example 2:

// BufferedReader is declared outside try() block
    BufferedReader br = new BufferedReader(new FileReader("C://readfile/input.txt"));

    try (BufferedReader inBr = br) {
            // ...
        }
    } catch (IOException e) {
        // ...
    }

In the above samples you can see if the object is ouside try then either we need to close manually or re-refer it. Also in the case of multiple objects in the try block, it looks messy and even if you declared inside try then you can't use outside try block.