Java Interview Questions
and Answers
How to delete a character in a String
✓~ Because Strings in Java are immutable. You'll have to create a new string removing
the character you don't want.
String newstr = str.substring(0, idx) + str.substring(idx + 1);
public String removeChar(String str, Integer n) {
String front = str.substring(0, n);
String back = str.substring(n+1, str.length());
return front + back;
}
What is Object Oriented Programming
✓~ Object-oriented programming (OOP) is a programming language model organized
around objects rather than "actions" and data rather than logic.
,The first step in OOP is to identify all the objects the programmer wants to
manipulate and how they relate to each other, an exercise often known as data
modeling.
What are be benefits of Object-Oriented Programming
✓~ Improved code reuse.
Improved software maintainability.
Faster development.
4 major principles that make a
language object-oriented.
✓~ Encapsulation, Data Abstraction, Polymorphism and Inheritence.
Describe the software development lifecycle
✓~ Communication, System concept development,
What is multithreading?
✓~ Multithreading is a process of executing multiple threads simultaneously. Its main
advantage is:
Threads share the same address space.
, Thread is lightweight.
Cost of communication between process is low.
What is thread?
✓~ A thread is a lightweight subprocess.It is a separate path of execution.It is called
separate path of execution because each thread runs in a separate stack frame.
What is difference between JDK,JRE and JVM?
✓~ JVM is an acronym for Java Virtual Machine, it is an abstract machine which provides
the runtime environment in which java bytecode can be executed. It is a specification.
JRE stands for Java Runtime Environment. It is the implementation of JVM.
JDK is an acronym for Java Development Kit. It physically exists. It contains JRE +
development tools.
How many types of memory areas are allocated by JVM?
✓~ Class(Method) Area
Heap
Stack
Program Counter Register
Native Method Stack
and Answers
How to delete a character in a String
✓~ Because Strings in Java are immutable. You'll have to create a new string removing
the character you don't want.
String newstr = str.substring(0, idx) + str.substring(idx + 1);
public String removeChar(String str, Integer n) {
String front = str.substring(0, n);
String back = str.substring(n+1, str.length());
return front + back;
}
What is Object Oriented Programming
✓~ Object-oriented programming (OOP) is a programming language model organized
around objects rather than "actions" and data rather than logic.
,The first step in OOP is to identify all the objects the programmer wants to
manipulate and how they relate to each other, an exercise often known as data
modeling.
What are be benefits of Object-Oriented Programming
✓~ Improved code reuse.
Improved software maintainability.
Faster development.
4 major principles that make a
language object-oriented.
✓~ Encapsulation, Data Abstraction, Polymorphism and Inheritence.
Describe the software development lifecycle
✓~ Communication, System concept development,
What is multithreading?
✓~ Multithreading is a process of executing multiple threads simultaneously. Its main
advantage is:
Threads share the same address space.
, Thread is lightweight.
Cost of communication between process is low.
What is thread?
✓~ A thread is a lightweight subprocess.It is a separate path of execution.It is called
separate path of execution because each thread runs in a separate stack frame.
What is difference between JDK,JRE and JVM?
✓~ JVM is an acronym for Java Virtual Machine, it is an abstract machine which provides
the runtime environment in which java bytecode can be executed. It is a specification.
JRE stands for Java Runtime Environment. It is the implementation of JVM.
JDK is an acronym for Java Development Kit. It physically exists. It contains JRE +
development tools.
How many types of memory areas are allocated by JVM?
✓~ Class(Method) Area
Heap
Stack
Program Counter Register
Native Method Stack
