Question

I was going thru ThreadLocal class and found below example

public class UniqueThreadIdGenerator {

 private static final AtomicInteger uniqueId = new AtomicInteger(0);

 private static final ThreadLocal < Integer > uniqueNum = 
     new ThreadLocal < Integer > () {
         @Override protected Integer initialValue() {
             return uniqueId.getAndIncrement();
     }
 };

 public static int getCurrentThreadId() {
     return uniqueId.get();
 }
} // UniqueThreadIdGenerator

Wondering the class ThreadLocal created above should be classified as inner class/anonymous class? Not Sure.

Answer 1

It’s an anonymous subclass of ThreadLocal.

An inner class is a class which is declared inside of another class declaration, using the class keyword. For example, Bar is an inner class of Foo below:

class Foo {
    int a;
    boolean b;

    class Bar {
        String s;
    }
}