State of design pattern - transportation
"Children crossing the road, left, red light stop, green light, Auntie is a baby." In order to give her clear, I specially to take her to see the running of the traffic light near our home. We all know that there are three status of traffic lights: redlights, yellowlights (Yellowlight) and green lights (Greenlight). The change in traffic lights is controlled by the control center (ControlCenter).
Let's take a look at how this process is implemented.
1, here, first define traffic lights (TrafficLight) interface class:
Public interface trafficLight {
Public void showredLight (); // Show red light
Public void showgreenlight (); // Show green light
Public void showyellowlight (); // Show yellow light
}
2, the traffic light near our home is the specific implementation of the TrafficLight interface of the Traffic Light: TRAFFICLIGHT:
Public class nearmyFamilyTraffiTriGHT IMPLEments TrafficLight {
Public void showredLight () {
System.out.println ("Red Light is on, you can't pass!");
}
Public void showgreenlight () {
System.out.println ("green light is bright, you can pass!");
}
Public void showyellowlight () {
System.out.println ("yellow light is bright!");
}
}
3. Define the Control Center class:
Public class controlcenter {
Private nearmyFamilyTraffiGHT TrafficLight; // Traffic lights near our home
Public void changestate (nearmyFamilyTraffiGht TrafficLight) {
THIS.TRAFFICLIGHT = TrafficLight;
}
Public void showredLight () {// Show red light
TrafficLight.showRedlight ();
}
Public void showgreenlight () {// Show green light
TrafficLight.showgreenlight ();
}
Public void showyellowlight () {// Show yellow light
TrafficLight.Showyellowlight ();
}
}
4, the traffic light near our home (NearmyFamilyTraffiTe is actually red, yellow, green three lamps:
A: Red Light (Redlight) class:
Public Class Redlight Extends NearmyFamilyTrafficLight {
Public static boolean existredLight = false;
Public static redlight getredlight () {// Get red light IF (EXISTREDLIGHT == false) {
EXISTREDLIGHT = TRUE;
Return new redlight ();
}
Return NULL;
}
}
B: Greenlight class:
Public class greenlight extends nearmyfamilytrafficLight {
Public static boolean existgreenlight = false;
Public static greenlight () {// Get green light
IF (existgreenlight == false) {
EXISTGREENLIGHT = TRUE;
Return new greenlight ();
}
Return NULL;
}
}
C: Yellow Light (Yellowlight) class:
Public Class Yellowlight Extends NearmyFamilyTraffiGHT {
Public static boolean existYellowlight = false;
Public Static Yellowlight getyellowlight () {// get yellow light
IF (existyellowlight == false) {
EXISTYELLOWLIGHT = TRUE;
Return New Yellowlight ();
}
Return NULL;
}
}
5, write test classes:
Public class test {
Public static void main (string args []) {
ControlCenter ControlCenter = New ControlCenter (); // Control Center
NearMyFamilyTrafficLight redLight = RedLight.getRedLight (); // Red NearMyFamilyTrafficLight greenLight = GreenLight.getGreenLight (); // green NearMyFamilyTrafficLight yellowLight = YellowLight.getYellowLight (); // yellow
ControlCenter.ChangeState (redlight); // change to red light status
ControlCenter.ShowRedlight (); // Show red light
ControlCenter.changeState (YELLOWLIGHT); / / Change into yellow light status
ControlCenter.Showyellowlight (); // Show yellow light
ControlCenter.changeState (Greenlight); // Change to green light status
ControlCenter.ShowGreenlight (); // Show green light
}
}
6. Description:
A: State definition: Different states, different behaviors; or, each state has the corresponding behavior.
B: We can see that the change in the state is a control center to control, and the normal operation of the traffic is implemented by displaying different lights.
C: Therefore, when there is a status to switch this matter, we can use State this mode.
