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Technical Question Bank : Core JAVA

Generally, technical interviews are conducted to assess candidates for technical or specialist job positions. These interviews test your field-specific technical knowledge. You need to be well-versed with the basic knowledge of Core JAVA. 
 
List of Technical Questions based on Core JAVA 
  • What is the most important feature of Java?
  • Explain platform independence
  • What is a JVM?
  • Are JVMs platform independent?
  • Differentiate between a JDK and a JVM?
  • What is a pointer? Does Java support pointers?
  • Name the base class of all classes
  • Is multiple inheritance supported by Java?
  • Is Java a purely object oriented language?
  • What are primitive data types in Arrays?
  • What is the difference between a Path and a Classpath?
  • What are local variables?
  • What are instance variables?
  • In Java, how is a constant variable defined?
  • Is it compulsory to use a main() method in all java classes?
  • What is the return type of the main() method?
  • What is the reason behind declaring the main() method static?
  • What is the argument of main() method?
  • Can we overload a main() method?
  • Can we declare a main() method final?
  • Does the order of public and static declaration matter in main() method?
  • Can a source file contain more than one class declaration?
  • What is a package?
  • Which package is imported by default?
  • Can a class that has been declared as private be accessed outside its package?
  • Can a class be declared as protected?
  • Elaborate the access scope of a protected method?
  • Elaborate the purpose of declaring a variable as final?
  • Explain impact of declaring a method as final?
  • If we do not want our class to be inherited by any other class what should we do?
  • Can you give few examples of final classes defined in Java API?
  • Differentiate final from finally and finalize()?
  • Can we declare a class as static?
  • When can a method be defined as static?
  • What are the restrictions imposed on a static method or a static block of code?
  • If you want to to print "Hello" even before main() is executed, how will you achieve that?
  • Explain the significance of static variable?
  • Can a static variable be declared inside a method?
  • What is an Abstract Class and what is its purpose?
  • Can an abstract class be declared final?
  • What is the use of an abstract variable?
  • Can you create an object of an abstract class?
  • Can an abstract class be defined without any abstract methods?
  • Class C implements Interface I containing method m1 and m2 declarations. Class C has provided implementation for method m2. Can i create an object of Class C?
  • Can a method inside an Interface be declared as final?
  • Can an Interface implement another Interface?
  • Can an Interface extend another Interface?
  • Can a Class extend more than one Class?
  • Why an Interface is able to extend more than one Interface but a Class cannot extend more than one Class?
  • Can an Interface be final?
  • Can a class be defined inside an Interface?
  • Can an Interface be defined inside a class?
  • What is a Marker Interface?
  • Overloading and Overriding achieve which all object oriented concepts?
  • Why is operator overloading not supported by JAVA?
  • Can private and protected modifiers be defined for variables in interfaces?
  • What is Externalizable?
  • What are the modifiers allowed for methods in an Interface?
  • What is a local, member and a class variable?
  • What is an abstract method?
  • What value does read() return when it reaches the end of a file?
  • Can you cast a Byte object to a double value?
  • Differentiate between a static and a non-static inner class?
  • What is an object's lock and which objects have locks?
  • What is the % operator?
  • When can an object reference be cast to an interface reference?
  • Which class is extended by all other classes?
  • Which non-Unicode letter characters may be used as the first character of an identifier?
  • What are the restrictions placed on method overloading?
  • What is casting?
  • What is the return type of a program's main() method?
  • Where can the variable be accessed when it is declared as private?
  • What do you understand by private, protected and public?
  • Explain Downcasting.
  • What modifiers may be used with an inner class that is a member of an outer class?
  • How many bits are used to represent Unicode, ASCII, UTF-16, and UTF-8 characters?
  • What are the restrictions placed on the location of a package statement within a source code file?
  • What is a native method?
  • What are order of precedence and associativity and how are they used?
  • Can an anonymous class be declared as implementing an interface and extending a class?
  • What is the range of the char type?
  • What is the range of the short type?
  • Why doesn't operator overloading exist?
  • What does it mean when we say that a method or field is "static"?
  • Is null a keyword?
  • Which characters may be used as the second but not as the first character of an identifier?
  • Is the ternary operator written x : y ? z or x ? y : z ?
  • How is rounding performed under integer division?
  • If a class is declared without any access modifiers, where may the class be accessed?
  • Does a class inherit the constructors of its superclass?
  • Name the eight primitive Java types.
  • What are the restrictions that are placed on the values of each case of a switch statement?
  • Differentiate between a while statement and a do while statement?
  • What all modifiers can be used with a local inner class?
  • When does the compiler supply a default constructor for a class?
  • Where may a method be accessed if it is declared as protected?
  • Elaborate the legal operands of the instance of operator?
  • Are true and false keywords?
  • What happens when you add a double value to a String?
  • Differentiate between inner class and nested class.
  • Can an abstract class be final?
  • What is numeric promotion?
  • Differentiate between a public and a non-public class?
  • To what value is a variable of the boolean type automatically initialized?
  • Differentiate between the prefix and postfix forms of the ++ operator.
  • What are the restrictions that are placed on method overriding?
  • What is a Java package and how is it used?
  • What modifiers may be used with a top-level class?
  • Differentiate between an if statement and a switch statement?
  • What are the practical benefits, if any, of importing a specific class rather than an entire package (e.g.
  • import java.net.* versus import java.net.Socket)?
  • Can we overload a method based on different return type but same argument type?
  • What happens to a static variable that is defined within a method of a class?
  • How many static initializers are there?
  • Differentiate between method overriding and overloading?
  • What is constructor chaining and how is it achieved in Java?
  • What is the difference between the Boolean & operator and the && operator?
  • Which Java operator is right associative?
  • Can a double value be cast to a byte?
  • What is the difference between a break statement and a continue statement?
  • Can a for statement loop indefinitely?
  • To what value is a variable of the String type automatically initialized?
  • Differentiate between a field variable and a local variable.
  • How are this() and super() used with constructors?
  • What does it mean that a class or member is final?
  • What does it mean that a method or class is abstract?
  • What is a transient variable?
  • How does Java handle integer overflows and underflows?
  • What is the difference between the >> and >>> operators?
  • Is size of a keyword?
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