Resolving IntelliJ Error for Try-With-Resources in JDK 7

What causes the IntelliJ error when using Try-Catch with Resources, and how can I resolve it?

try (BufferedReader br = new BufferedReader(new FileReader("file.txt"))) {
    String line;
    while ((line = br.readLine()) != null) {
        System.out.println(line);
    }
} catch (IOException e) {
    e.printStackTrace();
}

This error occurs when the IntelliJ IDEA project is configured to use a Java version that does not support the try-with-resources statement, which was introduced in Java 7. Here’s how to resolve this issue by ensuring your project is set to the correct Java version.

// Example of using try-with-resources in Java 7
try (BufferedReader br = new BufferedReader(new FileReader("myfile.txt"))) {
    String line;
    while ((line = br.readLine()) != null) {
        System.out.println(line);
    }
} catch (IOException e) {
    e.printStackTrace();
}

Causes

• The project is set to use an older Java version (e.g., 1.6) that does not support try-with-resources.
• The IntelliJ IDEA settings are misconfigured, preventing it from recognizing the correct Java SDK.

Solutions

• Open IntelliJ IDEA and navigate to `File -> Project Structure`.
• Under `Project`, ensure the 'Project SDK' is set to JDK 7 or higher.
• Select `Modules` in the Project Structure window, choose your module, and set the `Language level` to at least '7 - Diamond, try-with-resources'.
• If the SDK is not available, add it by clicking on `SDKs` and pointing to the JDK installation directory.
• Rebuild your project by selecting `Build -> Rebuild Project` to ensure the new settings take effect.

Mistake: Not updating IntelliJ's project settings after changing the Java version.

Solution: After installing a new JDK version, always check and reconfigure the project's SDK and language level settings.

Mistake: Using the wrong module configuration that doesn't match the project SDK.

Solution: Ensure that both project and module SDK settings are aligned with the installed JDK version.