The settings.json file is located in the user-level or workspace-level path and is used to customize VSCode settings. 1. User-level path: Windows is C:\Users\\AppData\Roaming\Code\User\settings.json, macOS is /Users//Library/ApplicationSupport/Code/User/settings.json, Linux is /home//.config/Code/User/settings.json; 2. Workspace-level path: .vscode/settings in the project root directory

To correctly handle JDBC transactions, you must first turn off the automatic commit mode, then perform multiple operations, and finally commit or rollback according to the results; 1. Call conn.setAutoCommit(false) to start the transaction; 2. Execute multiple SQL operations, such as INSERT and UPDATE; 3. Call conn.commit() if all operations are successful, and call conn.rollback() if an exception occurs to ensure data consistency; at the same time, try-with-resources should be used to manage resources, properly handle exceptions and close connections to avoid connection leakage; in addition, it is recommended to use connection pools and set save points to achieve partial rollback, and keep transactions as short as possible to improve performance.

itertools.combinations is used to generate all non-repetitive combinations (order irrelevant) that selects a specified number of elements from the iterable object. Its usage includes: 1. Select 2 element combinations from the list, such as ('A','B'), ('A','C'), etc., to avoid repeated order; 2. Take 3 character combinations of strings, such as "abc" and "abd", which are suitable for subsequence generation; 3. Find the combinations where the sum of two numbers is equal to the target value, such as 1 5=6, simplify the double loop logic; the difference between combinations and arrangement lies in whether the order is important, combinations regard AB and BA as the same, while permutations are regarded as different;

DependencyInjection(DI)isadesignpatternwhereobjectsreceivedependenciesexternally,promotingloosecouplingandeasiertestingthroughconstructor,setter,orfieldinjection.2.SpringFrameworkusesannotationslike@Component,@Service,and@AutowiredwithJava-basedconfi

fixture is a function used to provide preset environment or data for tests. 1. Use the @pytest.fixture decorator to define fixture; 2. Inject fixture in parameter form in the test function; 3. Execute setup before yield, and then teardown; 4. Control scope through scope parameters, such as function, module, etc.; 5. Place the shared fixture in conftest.py to achieve cross-file sharing, thereby improving the maintainability and reusability of tests.

Laravel's error and exception handling mechanism is based on the PHP exception system and Symfony component, and is managed uniformly by the App\Exceptions\Handler class. 1. Record exceptions through the report() method, such as integrating Sentry and other monitoring services; 2. Convert exceptions into HTTP responses through the render() method, supporting custom JSON or page jumps; 3. You can create custom exception classes such as PaymentFailedException and define their response format; 4. Automatically handle verification exception ValidationException, and manually adjust the error response structure; 5. Decide whether to display details based on the APP_DEBUG configuration.

TheJVMenablesJava’s"writeonce,runanywhere"capabilitybyexecutingbytecodethroughfourmaincomponents:1.TheClassLoaderSubsystemloads,links,andinitializes.classfilesusingbootstrap,extension,andapplicationclassloaders,ensuringsecureandlazyclassloa

When you cannot connect to the MySQL database, you should first check the connection string format and driver version. 1. Check whether the connection string format is correct. Common errors include port number, database name, parameter symbol errors and driver prefix errors. It is recommended to use the generation tool to verify the format and pay attention to escaping special characters; 2. Ensure that the correct JDBC or database driver is used, different drivers are used in different languages. Pay attention to version compatibility, dependency configuration and driver class name changes, and check the log to confirm whether the driver is loading successfully; 3. Check remote access permissions and firewall settings, including MySQL user permissions, bind-address configuration and server firewall rules, and need to open port 3306 and remote access permissions; 4. Use a simple test program to quickly verify the connection.