What is an object reference?
Ans : An object reference is essentially an object pointer with strong restrictions for integrity and safety. As a Java programmer, you can access objects (class instances and arrays) only by means of object references. Behind the scenes, an object reference provides two kinds of information to the run-time system: • a pointer to the object’s instance informationits data • a pointer to the object’s class informationits run-time type and its table of methods Although pointers exist inside the Java run-time system, you cannot manipulate them directly. The Java language does not expose a numerical notion of references or pointers: you cannot do pointer arithmetic, nor can you fabricate pointers from numeric data. The operations you can perform on an object reference all treat the reference as an opaque entity. Table 1.3, adapted from The Java Language Specification (p. 39), summarizes the possible operations on an object reference: Table 1.3: Possible Operations on an Object Reference ass
An object reference (REF) uniquely identify a row object stored in an object table or an object constructed from an object view. Typically, a REF value is comprised of the object’s unique identifier, the unique identifier associated with the object table, and the ROWID of the row in the object table in which the object is stored. The optional ROWID is used as a hint to provide fast access to the object.
