First of all check current java versions, run following command in the terminal
/usr/libexec/java_home -V
which will output something like the following:
Matching Java Virtual Machines (2): 9, x86_64: "Java SE 9" /Library/Java/JavaVirtualMachines/jdk-9.jdk/Contents/Home 1.8.0_152, x86_64: "Java SE 8" /Library/Java/JavaVirtualMachines/jdk1.8.0_152.jdk/Contents/Home