Set jdk version when building the project idea to compile java

One idea in mind to use its own module sdk compile the package can not find the cause of the problem.
Problem Description: sun.misc.base64decoder found.
Orientation: IDEA comes with jdk used to compile, resulting in some packages can not be found.
To solve the problem: file -> project structure -> module --- dependencies in the module sdk set to jdk8, the problem is solved.