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.
JRE (Java Runtime) is needed for running Java programs. JDK (Java Development Kit), which includes JRE plus the development tools (such as compiler and debugger), is need for writing as well as running Java programs. In other words, JRE is a subset of JDK. Since you are supposed to write Java Programs, you should install JDK, which includes JRE.