java.lang.UnsupportedClassVersionError: org/jetbrains/kotlin/preloading/Preloader : Unsupported major.minor version 52.0 while compile kotlin - kotlin

Question

I am beginner in Kotlin. I am getting the following exception while doing following:
kotlinc sample.kt -include-runtime -d sample.jar
Exception in thread "main" java.lang.UnsupportedClassVersionError:
org/jetbrains/kotlin/preloading/Preloader : Unsupported major.minor
version 52.0
at java.lang.ClassLoader.defineClass1(Native Method)
at java.lang.ClassLoader.defineClass(ClassLoader.java:800)
at java.security.SecureClassLoader.defineClass(SecureClassLoader.java:142)
at java.net.URLClassLoader.defineClass(URLClassLoader.java:449)
at java.net.URLClassLoader.access$100(URLClassLoader.java:71)
at java.net.URLClassLoader$1.run(URLClassLoader.java:361)
at java.net.URLClassLoader$1.run(URLClassLoader.java:355)
at java.security.AccessController.doPrivileged(Native Method)
at java.net.URLClassLoader.findClass(URLClassLoader.java:354)
at java.lang.ClassLoader.loadClass(ClassLoader.java:425)
at sun.misc.Launcher$AppClassLoader.loadClass(Launcher.java:308)
at java.lang.ClassLoader.loadClass(ClassLoader.java:358)
at sun.launcher.LauncherHelper.checkAndLoadMain(LauncherHelper.java:482)
Code
fun main(args: Array<String>){
var a : Int
a = getLength("Hello")
println("length of word is $a")
}
fun getLength(word : Any) : Int? {
if (word !is String) return null
return word.length
}
And kotlin version is Kotlin version 1.2.21-release-88 (JRE 1.7.0_79-b15)

Answer 1

JDK version which was used to build sample.jar is built with java version newr than one which you're using to compile kotlin file.
You have 2 ways:
Rebuild sample jar with your current version of JDK
Update JDK on your computer and try compiling again

Answer 2

Install an updated JDK, Go to File > Project Structure. Select the newer JDK version.
Then you'll be ready to go.