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98-372 · Question #33

Which of the following sample code segments demonstrates boxing?

The correct answer is C. int it = 12345;. Boxing is used to convert a value type to a reference type. In this sample code segment, the Integer object is a value type, and the instance of the Object class is a reference type. Converting from the value type to the reference type requires boxing. Boxing is an implicit conve

Understanding Data Types and Collections

Question

Which of the following sample code segments demonstrates boxing?

Options

  • Adouble dou = 12345;
  • Bobject obj = 12345;
  • Cint it = 12345;
  • Dint it = 12345;

How the community answered

(35 responses)
  • A
    3% (1)
  • B
    6% (2)
  • C
    77% (27)
  • D
    14% (5)

Explanation

Boxing is used to convert a value type to a reference type. In this sample code segment, the Integer object is a value type, and the instance of the Object class is a reference type. Converting from the value type to the reference type requires boxing. Boxing is an implicit conversion of a value type to a reference type. Consider the following declaration of a value type variable: The following statement implicitly applies the boxing operation on the variable test: object obj=test; This statement creates a reference to an object obj (on the stack) that references a value of the type int (on the heap). This value is a copy of the value-type value assigned to the variable test. It is not necessary to perform the boxing explicitly, as in the following example: object obj=(Object) test; Answer: A and D are incorrect. Converting between two value types requires neither boxing nor Answer: B is incorrect. Converting from a reference type to a value type is unboxing.

Topics

#boxing#value types#object type#type conversion

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