Core Java - Interview Questions and Answers


  1. What value does read() return when it has reached the end of a file?
    The read() method returns -1 when it has reached the end of a file.
  2. Can a Byte object be cast to a double value?
    No, an object cannot be cast to a primitive value.
  3. What is the difference between a static and a non-static inner class?
    A non-static inner class may have object instances that are associated with instances of the class's outer class. A static inner class does not have any object instances.
  4. What is an object's lock and which object's have locks?
    An object's lock is a mechanism that is used by multiple threads to obtain synchronized access to the object. A thread may execute a synchronized method of an object only after it has acquired the object's lock. All objects and classes have locks. A class's lock is acquired on the class's Class object.
  5. What is the % operator?
    It is referred to as the modulo or remainder operator. It returns the remainder of dividing the first operand by the second operand.
  6. When can an object reference be cast to an interface reference?
    An object reference be cast to an interface reference when the object implements the referenced interface.

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