After creating an Android Studio project, the ICU4J library will be added to the project Automatically.it increases the APK file size to 15 MB. I do not use this library, but I can not delete it.
You can see inside the APK Analyzer too:
How to remove the ICU4J library from the project
Check your Gradle file dependencies if there is dependency to icu4j remove it or if you are not using icu4j you can add
release {
minifyEnabled true
proguardFiles getDefaultProguardFile('proguard-android.txt'),
'proguard-rules.pro'
}
in your build configurations to remove unused code from your application.
or You can find shrinking code and resources documentation