how to reffer non static variable from static method?

Question

Q)i got one compile error 10::non-static variable this can not be refferenced from the static content

what to do now??

class Computer
{    
  void method()    
  {    
     System.out.println("this i objects");
  }


   public static void main(String[] args)    
    {    
      Laptop mtd = new Laptop();
      Computer mtd1 = new Computer();
      mtd.method();
      mtd1.method();
     }  


class Laptop
  {    
    void method()    
     {    
      System.out.println("using laptop method");         
     }    
  }    
}

i didnt gave that much space in original program @P45Imminent — borra
– borra, Commented Jul 9, 2015 at 11:46
So you added some for our pleasure? How can I express my gratitude? — P45 Imminent
– P45 Imminent, Commented Jul 9, 2015 at 11:46

Stephan Henningsen · Accepted Answer · 2015-08-30 19:47:15Z

1

Laptop is an inner class of Computer, thus you have to instantiate Laptop from a Computer instance. Or you can mark your inner Laptop class as static, then you can instantiate it directly. My example demonstrates both approaches:

class Computer
{

  public static void main(String[] args)
  {
      Computer computer = new Computer();
      computer.method();

      // Instantiate normal inner class from instance object.
      Laptop laptop = computer.new Laptop(); // Or: new Computer().new Laptop();
      laptop.method();

      // Instantiate static inner class directly.
      StaticLaptop staticLaptop = new StaticLaptop();
      staticLaptop.method();
  }

  void method()    
  {
      System.out.println("I'm Computer!");
  }


  class Laptop
  {
      void method()
      {
        System.out.println("I'm Laptop!");  
      }
  }

  static class StaticLaptop
  {
      void method()
      {
        System.out.println("I'm StaticLaptop!");  
      }
  }

}

edited Aug 30, 2015 at 19:47

answered Jul 9, 2015 at 11:53

Stephan Henningsen

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1 Comment

borra Over a year ago

thank you very munch for your information @stephen henningsen

P45 Imminent · Accepted Answer · 2015-07-09 11:53:20Z

0

You've put Laptop inside the Computer class.

You should refactor to static class Laptop. Otherwise you are tying a Laptop instance to a specific Computer instance, which you probably don't want to do. (If you really wanted to do that, you'd have to write new Computer().new Laptop();)

Although I think, in reality, you want to write

class Laptop extends Computer

which is called inheritance.

edited Jul 9, 2015 at 11:53

answered Jul 9, 2015 at 11:46

P45 Imminent

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2 Comments

borra Over a year ago

i am new to java language can u explian me what is refactor?? @p45Imminent

P45 Imminent Over a year ago

Just "change it to". That is, wack in the word static before your class Laptop

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