The capybara (Hydrochoerus hydrochaeris) is a large rodent of the genus Hydrochoerus of which the only other extant member is the lesser capybara (Hydrochoerus isthmius).
JDK is what gives the Java programming language its unique features of portability, security, simplicity, high performance, dynamism among others. With such features, it is no wonder as to why most developers opt to use Java when designing applications.
The Java Language is a language specification-you don't write a language in a language, it's a specification. That would be like asking Do you write French in German?. What I'm assuming the questioner really wanted to know is What language is the JDK developed in?.