What are the rules for external declarations in JShell in Java 9?

JShell is a command line tool introduced in Java 9, it is the first Java An official REPL tool for creating a simple programming environment that reads user input, evaluates it, and prints the results.

Declarations outside a class or interface (as well as declarations of classes and interfaces themselves) are created according to the following rules.

External declaration rules:

1) You can ignore public, protected and private etc. access modifier. All declaration fragments are accessible to all other fragments.

<strong>jshell> private int i = 10;
i ==> 10

jshell> System.out.println(i);
10</strong>

2) Modifierfinal can be ignored. Allows changes and inheritance.

<strong>jshell> final class A {void m() {} }
|   Warning:
|   Modifier &#39;final&#39; not permitted in top-level declarations, ignored
|   final class A {void m() {} }
|   ^---^
|   created class A</strong>

3) Modifier static can be ignored because there is no container class.

<strong>jshell> static char letter = &#39;A;
|   Warning:
|   Modifier &#39;static&#39; not permitted in top-level declarations, ignored
|   static char letter = &#39;A&#39;;
|   ^----^
letter ==> &#39;A&#39;</strong>

4) Do not allow the modifier's default and synchronization.

<strong>jshell> synchronized void method() {}
|   Error:
|   Modifier &#39;synchronized&#39; not permitted in top-level declarations
|   synchronized void method() {}
|   ^----------^</strong>

5) ModifierAbstract Allowed only within classes.

<strong>jshell> abstract void method();
|   Error:
|   Modifier &#39;abstract&#39; not permitted in top-level declarations
|   abstract void method();
|   ^------^</strong>

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