OnJava8-Examples/innerclasses/LocalInnerClass.java

// innerclasses/LocalInnerClass.java
// (c)2021 MindView LLC: see Copyright.txt
// We make no guarantees that this code is fit for any purpose.
// Visit http://OnJava8.com for more book information.
// Holds a sequence of Objects

interface Counter {
  int next();
}

public class LocalInnerClass {
  private int count = 0;
  Counter getCounter(final String name) {
    // A local inner class:
    class LocalCounter implements Counter {
      LocalCounter() {
        // Local inner class can have a constructor
        System.out.println("LocalCounter()");
      }
      @Override public int next() {
        System.out.print(name); // Access local final
        return count++;
      }
    }
    return new LocalCounter();
  }
  // Repeat, but with an anonymous inner class:
  Counter getCounter2(final String name) {
    return new Counter() {
      // Anonymous inner class cannot have a named
      // constructor, only an instance initializer:
      {
        System.out.println("Counter()");
      }
      @Override public int next() {
        System.out.print(name); // Access local final
        return count++;
      }
    };
  }
  public static void main(String[] args) {
    LocalInnerClass lic = new LocalInnerClass();
    Counter
      c1 = lic.getCounter("Local inner "),
      c2 = lic.getCounter2("Anonymous inner ");
    for(int i = 0; i < 5; i++)
      System.out.println(c1.next());
    for(int i = 0; i < 5; i++)
      System.out.println(c2.next());
  }
}
/* Output:
LocalCounter()
Counter()
Local inner 0
Local inner 1
Local inner 2
Local inner 3
Local inner 4
Anonymous inner 5
Anonymous inner 6
Anonymous inner 7
Anonymous inner 8
Anonymous inner 9
*/