设计模式 - 状态模式(state pattern) 未使用状态模式 详解

状态模式(state pattern) 未使用状态模式 详解

本文地址: http://blog.csdn.net/caroline_wendy

状态模式可以控制状态的转换, 未使用设计模式时, 程序会非常繁杂.

具体方法:
1. 状态转换类.
/**
* @time 2014年7月11日
*/
package state;

/**
* @author C.L.Wang
*
*/
public class GumballMachine {

final static int SOLD_OUT = 0;
final static int NO_QUARTER = 1;
final static int HAS_QUARTER = 2;
final static int SOLD = 3;

int state = SOLD_OUT;
int count = 0;

public GumballMachine(int count) {
this.count = count;
if (count > 0) {
state = NO_QUARTER; //转换模式
}
}

public void insertQuarter() { //输入25分钱
if (state == HAS_QUARTER) {
System.out.println("You can't insert another quarter.");
} else if (state == NO_QUARTER) {
state = HAS_QUARTER;
System.out.println("You inserted a quarter.");
} else if (state == SOLD_OUT) {
System.out.println("You can't insert a quarter, the machine is sold out.");
} else if (state == SOLD) {
System.out.println("Please wait, we're already giving you a gumball.");
}
}

public void ejectQuarter() { //退回25分钱
if (state == HAS_QUARTER) {
System.out.println("Quarter returned.");
state = NO_QUARTER;
} else if (state == NO_QUARTER) {
System.out.println("You haven't inserted a quarter.");
} else if (state == SOLD) {
System.out.println("Sorry, you already turned the crank.");
} else if (state == SOLD_OUT) {
System.out.println("You can't eject, you haven't inserted a quarter yet.");
}
}

public void turnCrank() { //摇动转杆
if (state == SOLD) {
System.out.println("Turning twice doesn't get another gumball.");
} else if (state == NO_QUARTER) {
System.out.println("You turned but there's no quarter.");
} else if (state == SOLD_OUT) {
System.out.println("You turned, but there are no gumballs");
} else if (state == HAS_QUARTER) {
System.out.println("You turned...");
state = SOLD;
dispense();
}
}

public void dispense() {
if (state == SOLD) {
System.out.println("A gumball comes rolling out the slot.");
count--;
if (count == 0) {
System.out.println("Opps, out of gumballs.");
state = SOLD_OUT;
} else {
state = NO_QUARTER;
}
} else if (state == NO_QUARTER) {
System.out.println("You need to pay first.");
} else if (state == SOLD_OUT) {
System.out.println("No gumball dispensed.");
} else if (state == HAS_QUARTER) {
System.out.println("No gumball dispensed.");
}
}

public void refill(int numGumballs) {
this.count = numGumballs;
state = NO_QUARTER;
}

public String toString() {
StringBuffer result = new StringBuffer();
result.append("\nMighty Gumball, Inc.");
result.append("\nJava-enabled Standing Gumball Model #2004\n");
result.append("Inventory: " + count + " gumball");
if (count != 1) {
result.append("s");
}
result.append("\nMachine is ");
if (state == SOLD_OUT) {
result.append("sold out.");
} else if (state == NO_QUARTER) {
result.append("waiting for quarter.");
} else if (state == HAS_QUARTER) {
result.append("waitring for turn of crank.");
} else if (state == SOLD) {
result.append("delivering a gumball.");
}
result.append("\n");
return result.toString();
}
}
2. 测试代码.
/**
* @time 2014年7月11日
*/
package state;

/**
* @author C.L.Wang
*
*/
public class GumballMachineTestDrive {

/**
* @param args
*/
public static void main(String[] args) {
// TODO Auto-generated method stub
GumballMachine gumballMachine = new GumballMachine(5);
System.out.println(gumballMachine);

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

System.out.println(gumballMachine);

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

System.out.println(gumballMachine);

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

System.out.println(gumballMachine);

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

System.out.println(gumballMachine);
}
}

3. 输出.
Mighty Gumball, Inc.
Java-enabled Standing Gumball Model #2004
Inventory: 5 gumballs
Machine is waiting for quarter.

You inserted a quarter.
You turned...
A gumball comes rolling out the slot.

Mighty Gumball, Inc.
Java-enabled Standing Gumball Model #2004
Inventory: 4 gumballs
Machine is waiting for quarter.

You inserted a quarter.
Quarter returned.
You turned but there's no quarter.

Mighty Gumball, Inc.
Java-enabled Standing Gumball Model #2004
Inventory: 4 gumballs
Machine is waiting for quarter.

You inserted a quarter.
You turned...
A gumball comes rolling out the slot.
You inserted a quarter.
You turned...
A gumball comes rolling out the slot.
You haven't inserted a quarter.

Mighty Gumball, Inc.
Java-enabled Standing Gumball Model #2004
Inventory: 2 gumballs
Machine is waiting for quarter.

You inserted a quarter.
You can't insert another quarter.
You turned...
A gumball comes rolling out the slot.
You inserted a quarter.
You turned...
A gumball comes rolling out the slot.
Opps, out of gumballs.
You can't insert a quarter, the machine is sold out.
You turned, but there are no gumballs

Mighty Gumball, Inc.
Java-enabled Standing Gumball Model #2004
Inventory: 0 gumballs
Machine is sold out.