kotlin-stdlib-jre7 is deprecated. Please use kotlin-stdlib-jdk7 instead

Important Update

Kotlin gradle config page has detailed information about this.

First of all check your kotlin version in gradle file.

if (kotlin_version == '1.2.x' ) (Use jdk NOT jre)

First check your jdk version in File > Project Structure.

Or check in build.gradle

compileOptions {
    sourceCompatibility JavaVersion.VERSION_1_8
    targetCompatibility JavaVersion.VERSION_1_8
}

if (jdk_version == 1.8)

implementation"org.jetbrains.kotlin:kotlin-stdlib-jdk8:$kotlin_version"

if (jdk_version == 1.7)

implementation"org.jetbrains.kotlin:kotlin-stdlib-jdk7:$kotlin_version"

if (jdk_version is < 1.7)

implementation"org.jetbrains.kotlin:kotlin-stdlib:$kotlin_version"

else if(NO jdk version is set in Project Structure)

if(Android_Studio_Version < 2.2.1){
   your_jdk_version = 1.7;
}
else {
   your_jdk_version = 1.8;
}

Because Android Studio is bundled with jdk 1.8 since 2.2.1 version.

2. else if ( kotlin_version == '1.1.x') (Use jre NOT jdk)

implementation"org.jetbrains.kotlin:kotlin-stdlib-jre7:$kotlin_version" // or jre8

You can update Kotlin version from Tools > Kotlin > Configure Kotlin Updates

Go to Tools > Kotlin > Configure Kotlin Plugin Updates and check for updates then in your app gradle file replace jre with jdk

implementation"org.jetbrains.kotlin:kotlin-stdlib-jdk7:$kotlin_version"

Newer version is jdk8

implementation"org.jetbrains.kotlin:kotlin-stdlib-jdk8:$kotlin_version"