What is the difference between a.getClass() and A.class in Java?

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I wouldn’t compare them in terms of pros/cons since they have different purposes and there’s seldom a “choice” to make between the two.

  • a.getClass() returns the runtime type of a. I.e., if you have A a = new B(); then a.getClass() will return the B class.

  • A.class evaluates to the A class statically, and is used for other purposes often related to reflection.

In terms of performance, there may be a measurable difference, but I won’t say anything about it because in the end it is JVM and/or compiler dependent.

This post has been rewritten as an article here.

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