Core Java - Interview Questions and Answers

  1. What is the difference between a public and a non-public class?
    A public class may be accessed outside of its package. A non-public class may not be accessed outside of its package.
  2. To what value is a variable of the boolean type automatically initialized?
    The default value of the boolean type is false.
  3. What is the difference between the prefix and postfix forms of the ++ operator?
    The prefix form performs the increment operation and returns the value of the increment operation. The postfix form returns the current value all of the expression and then performs the increment operation on that value.
  4. What restrictions are placed on method overriding?
    Overridden methods must have the same name, argument list, and return type. The overriding method may not limit the access of the method it overrides. The overriding method may not throw any exceptions that may not be thrown by the overridden method.
  5. What is a Java package and how is it used?
    A Java package is a naming context for classes and interfaces. A package is used to create a separate name space for groups of classes and interfaces. Packages are also used to organize related classes and interfaces into a single API unit and to control accessibility to these classes and interfaces.
  6. What modifiers may be used with a top-level class?
    A top-level class may be public, abstract, or final.

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