The State pattern

The state pattern, which closely resembles Strategy Pattern, is a behavioral software design pattern, also known as the objects for states pattern. This pattern is used in computer programming to represent the state of an object. This is a clean way for an object to partially change its type at runtime

interface State {

void writeName(StateContext stateContext, String name);

}

class StateA implements State {

public void writeName(StateContext stateContext, String name){

System.out.println(name.toLowerCase());

                stateContext.setState(new StateB());

}

}

class StateB implements State {

private int count=0;

public void writeName(StateContext stateContext, String name){

System.out.println(name.toUpperCase());

// change state after StateB's writeName() gets invoked twice

if(++count>1){

                        stateContext.setState(new StateA());

}

}

}

public class StateContext {

private State myState;

public StateContext(){

                setState(new StateA());

}

// normally only called by classes implementing the State interface

public void setState(State newState){

this.myState= newState;

}

public void writeName(String name){

this.myState.writeName(this, name);

}

}

public class TestClientState {

public static void main(String[] args){

                StateContext sc =new StateContext();

                sc.writeName("Monday");

                sc.writeName("Tuesday");

                sc.writeName("Wednesday");

                sc.writeName("Thursday");

                sc.writeName("Saturday");

                sc.writeName("Sunday");

}

}

According to the above code, the output of main() from TestClientState should be:

monday

TUESDAY

WEDNESDAY

thursday

SATURDAY

SUNDAY

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