Interfaces and polymorphism of integrated case

laptop

Notebook (laptop) usually have to use a USB device functions. In the production, notebooks have been reserved can insert a USB device's USB port, but specifically what USB devices, notebook manufacturers do not care, as long as compliant with the USB specification device can be. Defined USB interface, with the most basic function is turned on and off function. To be able to use the mouse and keyboard on the computer, the mouse and keyboard must also comply with the USB specification, to achieve a USB interface, the mouse and keyboard otherwise produced can not be used.

case study

• Described notebook class that implements the notebook using a USB mouse, USB keyboard
• USB interface, includes opening function, closing function
• Notebook class that contains the function run, shutdown function, a USB device functions
• Mouse class method, to achieve a USB interface, and have clicked
• Keyboard class, to achieve a USB interface, with percussion method

Case realization

USB interface definitions

Package demo07; 

public  interface the USB { 

    public  abstract  void Open (); // Open the device 

    public  abstract  void Close (); // Close device 

}

Mouse class definitions

Package demo07; 



// mouse USB device is a 
public  class Mouse the implements USB { 
    @Override 
    public  void Open () { 
        System.out.println ( "Mouse open" ); 
    } 

    @Override 
    public  void Close () { 
        System.out.println ( "off mouse" ); 
    } 

    public  void the click () { 
        System.out.println ( "mouse click" ); 
    } 
}

Keyboard class definitions

Package demo07; 


// keyboard USB device is a 
public  class Keyboard the implements USB { 
    @Override 
    public  void Open () { 
        System.out.println ( "keyboard open" ); 
    } 

    @Override 
    public  void Close () { 
        System.out.println ( "Close keyboard" ); 
    } 

    public  void type () { 
        System.out.println ( "input" ); 
    } 
}

Computer class definitions

Package demo07; 

public  class Computer { 

    public  void the powerOn () { 
        System.out.println ( "laptop boot" ); 
    } 

    public  void a powerOff () { 
        System.out.println ( "notebook is off" ); 
    } 

    // use the method of the USB device, the method using the interface as the parameter 
    public  void useDevice (USB USB) { 
        usb.open (); // open device 
        IF (USB the instanceof Mouse) { // sure Analyzing 
            Mouse mouse = (Mouse) usb; // downcast 
            mouse.click ();
        } The else IF (USB the instanceof Keyboard) { // first determine 
            Keyboard Keyboard = (Keyboard) USB; // downward transition 
            keyboard.type (); 
        } 
        usb.close (); // Close device 
    } 

}

Defines the test class

Package Penalty for demo07; 



public  class DemoMain { 

    public  static  void main (String [] args) {
         // First create a laptop 
        Computer Computer = new new Computer (); 
        computer.powerOn (); 

        // Prepare a mouse for computer use
 //         mouse mouse = new new mouse ();
         // firstly upward transition 
        USB usbmouse = new new mouse (); // multi-state writing
         // parameter is a USB type, I just passed into the USB mouse is 
        computer.useDevice (usbmouse); 

        / / create a USB keyboard 
        keyboard keyboard = new new keyboard ();// do not use multi-state writing
         // method USB type parameter is passed into the class object is to achieve 
        computer.useDevice (Keyboard); // correct wording! It has also undergone a transformation up
         // subclass objects, anonymous objects can also
 //         computer.useDevice (new new Keyboard ()); // is the correct wording 

        ; computer.powerOff () 
        System.out.println ( === " =============== " ); 

        Method ( 10.0); // correct wording, Double -> Double 
        Method (20 is); // correct wording, int -> Double 
        int A 30 = ; 
        Method (A); // correct wording, int -> Double 
    } 

    public  static void method(double num) {
        System.out.println(num);
    }

}

Results of the