There are several reasons for a method not to have a method body:

Noncompliant Code Example

public override function doSomething():void {
}

public function doSomethingElse():void {
}

Compliant Solution

public override function doSomething():void {
  throw new IllegalOperationError("doSomething cannot be performed because ...");
}

public function doSomethingElse():void {
  //This method is empty because ...
}