What are the 3 different contexts a class can be declared?

user_10226727 0
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I am told there are three different contexts in which a class can be declared in Java.
It has to do with the location within a program, but I can't think of what they are.

Obviously a class can be declared at the top of a page, the only other example I can think of is like a nested class?
I feel I may be going about this the wrong way.

class oop java
3 Answers

In a package

package com.example.mypackage;

public class TheClass {
}

In a class

package com.example.mypackage;

public class OuterClass {
    class InnerClass {
    }
}

Anonymously

public class MainClass {
    public static void main(String[] args) {
        AbstractClass myObject = new AbstractClass() {
            // overrides and other fields of the
            // anonymous class goes in this block
        };
    }
}

EDIT: As @daniu stated in the comment, a class can also be created in a method:

public class MainClass {
    public static void main(String[] args) {
        class MethodClass {
        }
        MethodClass myObject = new MethodClass();
    }
}
user_30917010

There are actually 4 distinct syntactic contexts:

  1. In the "compilation-unit" context; i.e. a top-level class declaration.

      package foo;
  public class Bar{}

  2. As a nested class declaration in a class declaration.

      package moo;
  public class Cow {
      public class Inner {}
  }

  3. As a nested class declaration in a method declaration.

      package too;
  public class Far {
      public void test() {
          class MethodInner{}
      }
  }

  4. As an anonymous class declaration in a new expression. The expression could appear in a variety of contexts. For example:

      package goo;
  public class Tar {
      public void test() {
          Runnable r = new Runnable() {
              public run() { }
          };
      }
  }
user_1399850

This may be what you are looking for:

public class TopLevel {

    public static void main(String[] args) {
        TopLevel topLevel = new TopLevel();
        Nested nested = new TopLevel.Nested();
        Inner inner = topLevel.new Inner();
    }

    public static class Nested {
    }

    public class Inner {
    }
}
user_58600730
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