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Tip of the Day
Language: Java Language
Expertise: Beginner
Jan 8, 1999

Variant Records

Question:
Does Java support an equivalent to the Pascal variant record or C union? I need to port some code to Java that uses these constructs.

Answer:
No, Java does not support the equivalent of variant records or unions. To achieve equivalent functionality, you can declare a class that contains all the fields you want. The disadvantage of this approach is that you don't get the memory space savings offered by variant records and unions. Also, it is not very object-oriented. Variant records and unions often are used to implement a form of polymorphism. The best way to port code that does this is to create a base class defining common methods and then derive several subclasses, one for each union field. Any code that operates on the data structures should do so by accessing the common virtual methods, rather than directly accessing the fields. If there is no usable polymorphism at work in your original code, then just separate out the variant record fields as separate data structures.

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