Which of the following is not a wildcard type in Java generics?Select one:a. -b. +c. *d. ?

Problem Breakdown

1. Identify the wildcard types in Java generics.
2. Determine which of the given options is not classified as a wildcard type.

Relevant Concepts

In Java generics, wildcards are used to represent an unknown type. The most common wildcard types include:

• Unbounded Wildcard: represented by ?
• Bounded Wildcards: represented by ? extends Type (upper bound) and ? super Type (lower bound). The symbols + and - are often associated with variance annotations in other programming languages, while the symbol * is not a recognized wildcard type in Java generics.

Analysis and Detail

• Option a: - is not a wildcard in Java.
• Option b: + is also not a wildcard in Java, but it represents covariance in relation to generics.
• Option c: * is not a wildcard in Java generics.
• Option d: ? is the valid wildcard in Java.

Verify and Summarize

Upon review of the options, both * and the symbols + and - are not used as wildcards in Java. However, the only valid Java wildcard is ?.

Final Answer

The correct answer is: **c. ***