Compiler Error J0175

Cannot invoke method on 'null' literal

The compiler detected an attempt to call a method from the null keyword. Null is not a class object and provides no methods. Remove the statement that attempted a method call from the null keyword and compile again.

The following example demonstrates this error:

public class Simple{
   public String methdo1(){
      //Do something meaningful here
      return null.toString(); 
      //error : cannot invoke a method from 'null'
   }
}