Johnson Controls Interview Questions and Answers

Objects of String are stored in the String Pool in Java.

• String objects are stored in the String Pool, a special memory area in Java heap memory.

• String literals are automatically stored in the String Pool.

• String objects created using the new keyword are not stored in the String Pool.

• String.intern() method can be used to store a String object in the String Pool.

Query parameters are used to pass data to a web server through the URL, while path parameters are part of the URL itself.

• Query parameters are key-value pairs added to the end of a URL after a '?'

• Path parameters are variables within the URL path itself, denoted by curly braces {}

• Example of query parameter: www.example.com/api/users?id=123

• Example of path parameter: www.example.com/api/users/{userId}

A bean in Spring Boot is a Java object that is instantiated, assembled, and managed by the Spring IoC container.

• Beans are defined in the Spring configuration file or using annotations like @Component, @Service, @Repository, etc.

• Beans are singleton by default but can be scoped as prototype, request, session, etc.

• Beans are injected into other beans using dependency injection.

• Example: @Component annotation is used to define a bean in Spring Boot.

HashMap is not thread-safe while ConcurrentHashMap is thread-safe.

• HashMap is not thread-safe and can cause ConcurrentModificationException if modified while iterating.

• ConcurrentHashMap allows concurrent modifications without causing any exception.

• ConcurrentHashMap achieves thread-safety by dividing the map into segments and locking only a portion of the map during updates.

• ConcurrentHashMap is suitable for high-concurrency scenarios where multiple threads are accessing and mod...read more

Exceptions are recoverable errors that can be handled in code, while errors are unrecoverable issues that usually result in program termination.

• Exceptions are checked at compile time, while errors are unchecked.

• Exceptions are subclasses of Throwable, while errors are subclasses of Error.

• Examples of exceptions include FileNotFoundException, NullPointerException, while examples of errors include OutOfMemoryError, StackOverflowError.