Method calls inside a Java class return an "identifier expected after this token" error

Solution 1:

The class body can only contain declarations.

Specifically, § 8.1.6 of the JLS defines the class body like this:

A class body may contain declarations of members of the class, that is, fields (§8.3), classes (§8.5), interfaces (§8.5) and methods (§8.4). A class body may also contain instance initializers (§8.6), static initializers (§8.7), and declarations of constructors (§8.8) for the class.

    ClassBody:
      { ClassBodyDeclarationsopt }

    ClassBodyDeclarations:
      ClassBodyDeclaration
      ClassBodyDeclarations ClassBodyDeclaration

    ClassBodyDeclaration:
      ClassMemberDeclaration
      InstanceInitializer
      StaticInitializer
      ConstructorDeclaration

    ClassMemberDeclaration:
      FieldDeclaration
      MethodDeclaration
      ClassDeclaration                        
      InterfaceDeclaration
      ;

As you can see, there are no statements in there anyway, so a class body may not directly contain a statement.

If you think about it, it makes sense: at which point should that code be executed? There is no context to tell you about that, so it makes no sense.

Solution 2:

This is illegal. In the class body you can have only: blocks, fields, constructors, methods and classes

Yours is neither. And what would you expect it to do anyway? If you want it to be executed when the class is instantiated, then place it in a block:

{
    System.currentTimeMillis();
}