Carelan Java Support Engineer Interview Questions and Answers

To create a Jar/war file, use the jar command in the terminal or an IDE like Eclipse.

• Use the jar command in the terminal to create a Jar file: jar cf jarFileName.jar file1 file2

• Use the jar command with 'war' option to create a War file: jar cf warFileName.war file1 file2

• In Eclipse, right-click on the project, go to Export > JAR file/WAR file, and follow the prompts

I will use logging, debugging tools like breakpoints, and analyzing stack traces to identify and fix issues in the code.

• Use logging statements to track the flow of the code and identify any unexpected behavior.

• Set breakpoints in the code to pause execution at specific points and inspect variables and data.

• Analyze stack traces to understand the sequence of method calls leading to an error.

• Use debugging tools like Eclips...read more

Use the put() method to replace a value in a HashMap.

• Use the put() method with the key of the value you want to replace

• Example: map.put(key, newValue);

Front end communicates with the backend in Spring through HTTP requests using RESTful APIs.

• Front end sends HTTP requests to the backend server

• Backend server processes the requests and sends back HTTP responses

• Communication is typically done using RESTful APIs in Spring MVC

• Data is exchanged in JSON format between front end and backend

To fetch a value from application.properties file in Spring Boot, use @Value annotation or Environment object.

• Use @Value annotation to inject values directly into a field

• Use Environment object to access properties programmatically

• Example: @Value("${my.property}") private String myProperty;

• Example: @Autowired private Environment env; String propertyValue = env.getProperty("my.property");

Some annotations in Spring Boot are @RestController, @Autowired, @Component, @RequestMapping, @Service.

• @RestController - used to define RESTful web services.

• @Autowired - used for automatic dependency injection.

• @Component - marks a java class as a bean so that the component-scanning mechanism of Spring can pick it up and pull it into the application context.

• @RequestMapping - used to map web requests to specific handler ...read more

You can change the data type of a column in SQL using the ALTER TABLE statement.

• Use the ALTER TABLE statement followed by the MODIFY COLUMN clause to change the data type of a column.

• Specify the new data type for the column after the MODIFY COLUMN clause.

• Make sure to handle any data conversion or potential data loss when changing the data type.

You can pull the pids of Java processes using command line tools like jps or ps.

• Use 'jps' command to list Java processes along with their pids.

• Use 'ps -ef | grep java' command to list all processes with 'java' in their name and find the pid.

• You can also use tools like VisualVM or JConsole to monitor and manage Java processes.

To reduce heap memory usage in Java, you can optimize code, limit object creation, use data structures efficiently, and tune JVM settings.

• Optimize code by avoiding unnecessary object creation and using efficient algorithms

• Limit object creation by reusing objects, using object pooling, or implementing flyweight design pattern

• Use data structures efficiently by choosing the right data structure for the task at hand

• Tune JV...read more

mvn clean install is a Maven command used to clean the project, compile the source code, run tests, and package the application.

• Removes target directory to clean project

• Compiles the source code

• Runs tests

• Packages the application

• Dependencies are downloaded if needed