在UML當中有狀態機視圖,這個狀態機可以用於自動售貨機,自動售票機等等場景,下面是用java代碼模擬的一個狀態機:
1.狀態機接口
package stateMachine;
/**
* 狀態機接口
* @author seacean
* @date 2013-8-29
*/
public interface State {
/**
* 投入硬幣
*/
void insertQuarter();
/**
* 根據搖動情況,處理搖動結果,返回處理結果,釋放糖果
*/
void ejectQuarter();
/**
* 轉動搖柄
*/
void turnCrank();
/**
* 機器放出糖果,處理機器內部狀態,返回初始可投幣狀態
*/
void dispense();
}
2.帶有狀態機的機器
package stateMachine;
/**
* 機器類,包含多種狀態,處理流程
* @author seacean
* @date 2013-8-29
*/
public class Machine {
//機器本身包含所有的狀態機
private State soldOutState;
private State noQuarterState;
private State hasQuarterState;
private State soldState;
private State state; //機器的當前狀態
private int count = 0;//機器中當前糖果的數量
/**
* 初始化機器,引入所有的狀態機,初始化糖果數量,初始化機器狀態
* @param count
*/
public Machine(int count) {
this.soldOutState = new SoldOutState(this);
this.noQuarterState = new NoQuarterState(this);
this.hasQuarterState = new HasQuarterState(this);
this.soldState = new SoldState(this);
this.count = count;
if (this.count > 0) {
this.state = noQuarterState;
}
}
/**
* 釋放糖果時的內部處理程序
*/
public void releaseBall() {
System.out.println("a gumball comes rolling out the solt...");
if (count > 0) {
count -= 1;
}
}
public void insertQuerter() {
state.insertQuarter();//加入硬幣
}
public void ejectQuarter() {
state.ejectQuarter();
}
public void turnCrank() {
state.turnCrank();
state.dispense();
}
public State getSoldOutState() {
return soldOutState;
}
public State getNoQuarterState() {
return noQuarterState;
}
public State getHasQuarterState() {
return hasQuarterState;
}
public State getSoldState() {
return soldState;
}
public State getState() {
return state;
}
public int getCount() {
return count;
}
public void setState(State state) {
this.state = state;
}
}
3.下面是狀態機的一些實現類
package stateMachine;
/**
* 機器處於沒有投硬幣的狀態
* @author seacean
* @date 2013-8-29
*/
public class NoQuarterState implements State {
private Machine machine;
public NoQuarterState(Machine machine) {
this.machine = machine;
}
@Override
public void insertQuarter() {
System.out.println("please insert a quarter!");
machine.setState(machine.getHasQuarterState());
}
@Override
public void ejectQuarter() {
System.out.println("please insert a quarter!");
}
@Override
public void turnCrank() {
System.out.println("please insert a quarter!");
}
@Override
public void dispense() {
System.out.println("please insert a quarter!");
}
}
package stateMachine;
/**
* 機器處於有硬幣,有糖果,沒有搖動的狀態
* @author seacean
* @date 2013-8-29
*/
public class HasQuarterState implements State {
private Machine machine;
public HasQuarterState(Machine machine){
this.machine=machine;
}
@Override
public void insertQuarter() {
System.out.println("You can not insert another quarter!");
}
@Override
public void ejectQuarter() {
System.out.println("Quarter returned!");
machine.setState(machine.getNoQuarterState());
}
@Override
public void turnCrank() {
System.out.println("You turned ... ");
machine.setState(machine.getSoldState());
}
@Override
public void dispense() {
System.out.println("No gumball dispensed!");
}
}
package stateMachine;
/**
* 機器正在出售糖果的狀態
*
* @author seacean
* @date 2013-8-29
*/
public class SoldState implements State {
private Machine machine;
public SoldState(Machine machine) {
this.machine = machine;
}
@Override
public void insertQuarter() {
System.out.println("please wait,we are already giving you a gumball!");
}
@Override
public void ejectQuarter() {
System.out.println("Sorry, you have turned the crank!");
}
@Override
public void turnCrank() {
System.out.println("Turning twice does not get you another gumball!");
}
@Override
public void dispense() {
machine.releaseBall();
if (machine.getCount() > 0) {
machine.setState(machine.getNoQuarterState());
} else {
System.out.println("Out of Gumballs!");
machine.setState(machine.getSoldOutState());
}
}
}
package stateMachine;
/**
* 機器處於無糖果狀態
* @author seacean
* @date 2013-8-29
*/
public class SoldOutState implements State {
private Machine machine;
public SoldOutState(Machine machine) {
this.machine=machine;
}
@Override
public void insertQuarter() {
System.out.println("Sorry, there is no gumball in the machine!");
}
@Override
public void ejectQuarter() {
System.out.println("Sorry, there is no gumball in sold!");
}
@Override
public void turnCrank() {
System.out.println("Sorry, there is no gumball!Turn is no meaning.");
machine.setState(machine.getNoQuarterState());
}
@Override
public void dispense() {
System.out.println("Sorry, there is no gumball!");
}
}
4.下面是測試類
package stateMachine;
//測試類
public class StateMachineTest {
public static void main(String[] args) {
Machine machine=new Machine(10);
for(int i=0;i<11;i++){
System.out.println(machine);
machine.insertQuerter();
machine.turnCrank();
}
}
}