isHighSurrogate  
  Since Kotlin
1.0Returns true if this character is a Unicode high-surrogate code unit (also known as leading-surrogate code unit).
Since Kotlin
1.1Returns true if this character is a Unicode high-surrogate code unit (also known as leading-surrogate code unit).
Since Kotlin
1.0Returns true if this character is a Unicode high-surrogate code unit (also known as leading-surrogate code unit).