How to create instances of static nested classes and inner classes?

The semantics for creating instances of static nested classes/inner classes can be confusing.

• creating an instance of the inner class requires a reference to an instance of the enclosing class
• creating an instance of the static nested class does not require an instance of the enclosing class

Here is an example which is a simple class that defines a static nested class and an inner class:

public class EnclosingClass {
    private String name = "instance name";
    private static String staticName = "static name";

    public static void main(String[] args) {
       EnclosingClass enclosingClass = new  EnclosingClass();
       EnclosingClass.InnerClass innerClass = enclosingClass.new InnerClass();
       EnclosingClass.StaticNestedClass staticNestedClass 
            = new EnclosingClass.StaticNestedClass();
    }
    
    class InnerClass {
       InnerClass() {
          System.out.println(name);
          System.out.println(staticName);
       }
    }
    static class StaticNestedClass {
       StaticNestedClass() {
          System.out.println(staticName);
       }
    }
}

Nested classes can be confusing, but once you understand their purpose and get used to the semantics, there isn't a lot to them. If you'd like to learn more about the details of nested classes, check out the Nested Classes in XyzWS SCJP section.

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