Interview questions for Java, 2022
What is Java?
Answer: Java is an object-oriented, high-level, general-purpose programming language originally designed by James Gosling and further developed by the Oracle Corporation. It is one of the most popular programming languages in the world.
Explain about Java Virtual Machine?
Answer: JVM is a program that interprets the intermediate Java byte code and generates the desired output. It is because of byte code and JVM that programs written in Java are highly portable.
What is an Object?
Answer: An instance of a Java class is known as an object. Two important properties of a Java object are behaviour and state. An object is created as soon as the JVM comes across the new keyword.
Define classes in Java
Answer: A class is a collection of objects of similar data types. Classes are user-defined data types and behave like built-in types of a programming language.
What is the JIT compiler?
Answer: JIT compiler runs after the program is executed and compiles the code into a faster form, hosting CPU’s native instructing set. JIT can access dynamic runtime information, whereas a standard compiler doesn’t and can make better optimizations like inlining functions that are used frequently.
Explain Typecasting?
Answer: The concept of assigning a variable of one data type to a variable of another data type. It is not possible for the boolean data type.
It is of two types:
- Implicit
- Explicit
Define classes in Java
Answer: A class is a collection of objects of similar data types. Classes are user-defined data types and behave like built-in types of a programming language.
What is the JIT compiler?
Answer: JIT compiler runs after the program is executed and compiles the code into a faster form, hosting CPU’s native instructing set. JIT can access dynamic runtime information, whereas a standard compiler doesn’t and can make better optimizations like inlining functions that are used frequently.
Which Java IDE to use, and why?
Answer: A Java IDE is a software that allows Java developers to easily write as well as debug Java programs. It is basically a collection of various programming tools, accessible via a single interface, and several helpful features, such as code completion and syntax highlighting. Codenvy, Eclipse, and NetBeans are some of the most popular Java IDEs.
Java is a platform-independent language. Why?
Answer: Java programming language does not depend on any particular hardware or software because it is compiled by the compiler and then converted into byte code. Byte code is platform-independent and can run on multiple systems. The only requirement is Java needs a runtime environment, i.e., JRE, which is a set of tools used for developing Java applications.
What are the default values for local variables?
Answer: The local variables are not initialized to any default value, neither primitives nor object references.
What gives Java its ‘write once and run anywhere’ nature?
The bytecode. Java compiler converts the Java programs into the class file (Byte Code) which is the intermediate language between source code and machine code. This bytecode is not platform specific and can be executed on any computer.
Why Java is not 100% Object-oriented?
Java is not 100% Object-oriented because it makes use of eight primitive data types such as boolean, byte, char, int, float, double, long, short which are not objects.
What is a Map in Java?
In Java, Map is an interface of Util package which maps unique keys to values. The Map interface is not a subset of the main Collection interface and thus it behaves little different from the other collection types
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