Java Developer

JVM (Java Virtual Machine) is an abstract machine. It is a specification that provides runtime environment in which java bytecode can be executed.
It is:
1. A specification where working of Java Virtual Machine is specified. But implementation provider is independent to choose the algorithm. Its implementation has been provided by Oracle and other companies.
2. An implementation Its implementation is known as JRE (Java Runtime Environment).
3. Runtime Instance Whenever you write java command on the command prompt to run the java class, an instance of JVM is created.

A Java™ runtime environment (JRE) is a set of components to create and run a Java application. A JRE is part of a Java development kit (JDK). A JRE is made up of a Java virtual machine (JVM), Java class libraries, and the Java class loader. JDKs are used to develop Java software; JREs provide programming tools and deployment technologies; and JVMs execute Java programs.

The new operator is an operator which denotes a request for memory allocation on the Heap. If sufficient memory is available, new operator initializes the memory and returns the address of the newly allocated and initialized memory to the pointer variable. When you create an object of class using new keyword(normal new).
The memory for the object is allocated using operator new from heap.
The constructor of the class is invoked to properly initialize this memory.

1. MongoDB is an open-source database developed by MongoDB, Inc. MongoDB stores data in JSON-like documents that can vary in structure. It is a popular NoSQL database. MySQL is a popular open-source relational database management system (RDBMS) that is developed, distributed and supported by Oracle Corporation.
2. In MongoDB, each individual records are stored as ‘documents’. In MySQL, each individual records are stored as ‘rows’ in a table.
3. Documents belonging to a particular class or group as stored in a ‘collection’ in MongoDB. Example: collection of users. A ‘table’ is used to store rows (records) of similar type in MYSQL.
4. MongoDB is what is called a NoSQL database. This means that pre-defined structure for the incoming data can be defined and adhered to but also, if required different documents in a collection can have different structures. It has a dynamic schema. MySQL as the name suggests uses Structured Query Language (SQL) for database access. The schema can not be changed. The inputs following the given schema are only entered.

Tip 1 : The cross questioning can go intense some time, think before you speak.

Tip 2 : Be open minded and answer whatever you are thinking, in these rounds I feel it is important to have opinion.

Tip 3 : Context of questions can be switched, pay attention to the details. It is okay to ask questions in these round, like what are the projects currently the company is investing, which team you are mentoring. How all is the work environment etc.