Head First设计模式-状态模式

一、整体代码

       State.java

public interface State {

public void insertQuarter();
public void ejectQuarter();
public void turnCrank();
public void dispense();
}

       SoldState.java

public class SoldState implements State {
    GumballMachine gumballMachine;

    public SoldState(GumballMachine gumballMachine) {
        this.gumballMachine = gumballMachine;
    }

public void insertQuarter() {
System.out.println("Please wait, we're already giving you a gumball");
}

public void ejectQuarter() {
System.out.println("Sorry, you already turned the crank");
}

public void turnCrank() {
System.out.println("Turning twice doesn't get you another gumball!");
}

public void dispense() {
gumballMachine.releaseBall();
if (gumballMachine.getCount() > 0) {
gumballMachine.setState(gumballMachine.getNoQuarterState());
} else {
System.out.println("Oops, out of gumballs!");
gumballMachine.setState(gumballMachine.getSoldOutState());
}
}

public String toString() {
return "dispensing a gumball";
}
}

      SoldOutState.java

public class SoldOutState implements State {
    GumballMachine gumballMachine;

    public SoldOutState(GumballMachine gumballMachine) {
        this.gumballMachine = gumballMachine;
    }

public void insertQuarter() {
System.out.println("You can't insert a quarter, the machine is sold out");
}

public void ejectQuarter() {
System.out.println("You can't eject, you haven't inserted a quarter yet");
}

public void turnCrank() {
System.out.println("You turned, but there are no gumballs");
}

public void dispense() {
System.out.println("No gumball dispensed");
}

public String toString() {
return "sold out";
}
}

      NoQuarterState.java

public class NoQuarterState implements State {
    GumballMachine gumballMachine;

    public NoQuarterState(GumballMachine gumballMachine) {
        this.gumballMachine = gumballMachine;
    }

public void insertQuarter() {
System.out.println("You inserted a quarter");
gumballMachine.setState(gumballMachine.getHasQuarterState());
}

public void ejectQuarter() {
System.out.println("You haven't inserted a quarter");
}

public void turnCrank() {
System.out.println("You turned, but there's no quarter");
 }

public void dispense() {
System.out.println("You need to pay first");
} 

public String toString() {
return "waiting for quarter";
}
}

     HasQuarterState.java

import java.util.Random;

public class HasQuarterState implements State {
Random randomWinner = new Random(System.currentTimeMillis());
GumballMachine gumballMachine;

public HasQuarterState(GumballMachine gumballMachine) {
this.gumballMachine = gumballMachine;
}

public void insertQuarter() {
System.out.println("You can't insert another quarter");
}

public void ejectQuarter() {
System.out.println("Quarter returned");
gumballMachine.setState(gumballMachine.getNoQuarterState());
}

public void turnCrank() {
System.out.println("You turned...");
int winner = randomWinner.nextInt(10);
if ((winner == 0) && (gumballMachine.getCount() > 1)) {
gumballMachine.setState(gumballMachine.getWinnerState());
} else {
gumballMachine.setState(gumballMachine.getSoldState());
}
}

    public void dispense() {
        System.out.println("No gumball dispensed");
    }

public String toString() {
return "waiting for turn of crank";
}
}

     WinnerState.java

public class WinnerState implements State {
    GumballMachine gumballMachine;

    public WinnerState(GumballMachine gumballMachine) {
        this.gumballMachine = gumballMachine;
    }

public void insertQuarter() {
System.out.println("Please wait, we're already giving you a Gumball");
}

public void ejectQuarter() {
System.out.println("Please wait, we're already giving you a Gumball");
}

public void turnCrank() {
System.out.println("Turning again doesn't get you another gumball!");
}

public void dispense() {
System.out.println("YOU'RE A WINNER! You get two gumballs for your quarter");
gumballMachine.releaseBall();
if (gumballMachine.getCount() == 0) {
gumballMachine.setState(gumballMachine.getSoldOutState());
} else {
gumballMachine.releaseBall();
if (gumballMachine.getCount() > 0) {
gumballMachine.setState(gumballMachine.getNoQuarterState());
} else {
            System.out.println("Oops, out of gumballs!");
gumballMachine.setState(gumballMachine.getSoldOutState());
}
}
}

public String toString() {
return "despensing two gumballs for your quarter, because YOU'RE A WINNER!";
}
}

      GumballMachine.java

public class GumballMachine {

State soldOutState;
State noQuarterState;
State hasQuarterState;
State soldState;
State winnerState;

State state = soldOutState;
int count = 0;

public GumballMachine(int numberGumballs) {
soldOutState = new SoldOutState(this);
noQuarterState = new NoQuarterState(this);
hasQuarterState = new HasQuarterState(this);
soldState = new SoldState(this);
winnerState = new WinnerState(this);

this.count = numberGumballs;
 if (numberGumballs > 0) {
state = noQuarterState;
} 
}

public void insertQuarter() {
state.insertQuarter();
}

public void ejectQuarter() {
state.ejectQuarter();
}

public void turnCrank() {
state.turnCrank();
state.dispense();
}

void setState(State state) {
this.state = state;
}

void releaseBall() {
System.out.println("A gumball comes rolling out the slot...");
if (count != 0) {
count = count - 1;
}
}

int getCount() {
return count;
}

void refill(int count) {
this.count = count;
state = noQuarterState;
}

    public State getState() {
        return state;
    }

    public State getSoldOutState() {
        return soldOutState;
    }

    public State getNoQuarterState() {
        return noQuarterState;
    }

    public State getHasQuarterState() {
        return hasQuarterState;
    }

    public State getSoldState() {
        return soldState;
    }

    public State getWinnerState() {
        return winnerState;
    }

public String toString() {
StringBuffer result = new StringBuffer();
result.append("\nMighty Gumball, Inc.");
result.append("\nJava-enabled Standing Gumball Model #2004");
result.append("\nInventory: " + count + " gumball");
if (count != 1) {
result.append("s");
}
result.append("\n");
result.append("Machine is " + state + "\n");
return result.toString();
}
}

     GumballMachineTestDrive.java

public class GumballMachineTestDrive {

public static void main(String[] args) {
GumballMachine gumballMachine = 
new GumballMachine(10);

System.out.println(gumballMachine);

gumballMachine.insertQuarter();
gumballMachine.turnCrank();
gumballMachine.insertQuarter();
gumballMachine.turnCrank();

System.out.println(gumballMachine);

gumballMachine.insertQuarter();
gumballMachine.turnCrank();
gumballMachine.insertQuarter();
gumballMachine.turnCrank();

System.out.println(gumballMachine);

gumballMachine.insertQuarter();
gumballMachine.turnCrank();
gumballMachine.insertQuarter();
gumballMachine.turnCrank();

System.out.println(gumballMachine);

gumballMachine.insertQuarter();
gumballMachine.turnCrank();
gumballMachine.insertQuarter();
gumballMachine.turnCrank();

System.out.println(gumballMachine);

gumballMachine.insertQuarter();
gumballMachine.turnCrank();
gumballMachine.insertQuarter();
gumballMachine.turnCrank();

System.out.println(gumballMachine);
}
}

二、解释

       状态模式：允许对象在内部对象改变时改变它的行为，对象好像修改了他的类。