What is the use of Java libraries?

The library provides an abstract interface to tasks that would normally depend heavily on the hardware and operating system, such as network access and file access . Some underlying platforms may not support all of the features a Java application expects.

Flutter uses a flexible system that allows you to call platform-specific APIs in a language that works directly with those APIs: Kotlin or Java on Android.

There is no way you can use any java-related code or application in iOS . You have to work on a native port. iOS doesn’t have a jvm.