Taj Techno Interview Questions and Answers

To run a Java program using command line, use the 'java' command followed by the name of the class containing the main method.

• Navigate to the directory containing the .class file

• Type 'java' followed by the name of the class containing the main method

• Include any necessary command line arguments after the class name

• Press enter to run the program

• Example: java MyProgram arg1 arg2

Classloader is a part of JVM that loads classes into memory. It has three types: Bootstrap, Extension, and Application.

• Classloader loads classes into memory when they are needed by the program

• Bootstrap classloader loads core Java classes from the JDK's rt.jar file

• Extension classloader loads classes from the JDK's lib/ext directory

• Application classloader loads classes from the classpath of the application

• Classloader follows delegation model to load classes

Hashmap and Hashtable are both used to store key-value pairs, but Hashtable is synchronized and slower than Hashmap.

• Hashmap is not synchronized and allows null keys/values.

• Hashtable is synchronized and does not allow null keys/values.

• Hashmap is faster than Hashtable.

• Hashmap is preferred for non-threaded applications.

• Hashtable is preferred for threaded applications.

• Example: HashMap map = new HashMap<>();

• Example: Hashtable table = new Hashtable<>();

Hashmap is a data structure that stores key-value pairs and uses hashing to retrieve values quickly.

• Hashmap uses an array to store the key-value pairs

• The key is hashed to find the index in the array where the value is stored

• If two keys hash to the same index, a linked list is used to store multiple values

• Hashmap uses load factor to determine when to resize the array

• Hashmap provides constant time complexity for insertion, deletion, and retrieval

A defect is an error or flaw in a software application that causes it to behave unexpectedly or not as intended.

• Defects can be caused by coding errors, design flaws, or environmental factors.

• Defects can lead to system crashes, data corruption, or security vulnerabilities.

• Examples of defects include syntax errors, logic errors, and performance issues.

• Defects can be identified through testing, debugging, and code reviews.