浅析设计模式之八状态模式

Posted 2020-09-28

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传统的状态大都是这样的(状态模式)

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;
    
    
    
}

然后嵌入大量的if - else

根究当前状态来进行某些操作,但是呢,现在我们是学过设计模式的人了,我们总是想搞出点幺蛾子来封装一下我们想要的东西,换句话说,我们要遵守"封装变化"原则

创建一个接口,填充我们需要的某些行为

/**
 * 状态接口
 * @author Dougest 2017年7月16日    下午11:19:57
 *
 */
public interface State {
    void insertQuarter();
    void ejectQuarter();
    void turnCrank();
    void dispense();
}

然后通过几个实现类来实现我们不同状态写的具体细节

/**
 * 状态实现类
 * @author Dougest 2017年7月16日    下午11:19:57
 *
 */
public class SoldState {
    void insertQuarter();
    void ejectQuarter();
    void turnCrank();
    void dispense();
}

/**
 * 状态实现类
 * @author Dougest 2017年7月16日    下午11:19:57
 *
 */
public class SoldOutState {
    void insertQuarter();
    void ejectQuarter();
    void turnCrank();
    void dispense();
}

/**
 * 状态实现类
 * @author Dougest 2017年7月16日    下午11:19:57
 *
 */
public class NoQuarterState {
    void insertQuarter();
    void ejectQuarter();
    void turnCrank();
    void dispense();
}

/**
 * 状态实现类
 * @author Dougest 2017年7月16日    下午11:19:57
 *
 */
public class HasQuarterState {
    void insertQuarter();
    void ejectQuarter();
    void turnCrank();
    void dispense();
}

现在来具体实现

接口不变,实现新的调用类

/**
 * 
 * @author Dougest 2017年7月17日    上午12:10:47
 *
 */
public class CompleMachine {
    State noQuarterState;
    State hasQuarterState;
    State soldOutState;
    State soldState;
    
    State state = soldOutState;
    int count = 0;
    
    
    public CompleMachine(int numberCompleMachine) {
        noQuarterState = new NoQuarterState(this);
        hasQuarterState = new HasQuarterState(this);
        soldOutState = new SoldOutState(this);
        soldState = new SoldState(this);
        this.count = numberCompleMachine;
        
        if(numberCompleMachine > 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() {
        if(count != 0)
            count = count -1;
    }
    
    public int getCount() {
        return this.count;
    }
    public State getNoQuarterState() {
        return noQuarterState;
    }
    public void setNoQuarterState(State noQuarterState) {
        this.noQuarterState = noQuarterState;
    }
    public State getHasQuarterState() {
        return hasQuarterState;
    }
    public void setHasQuarterState(State hasQuarterState) {
        this.hasQuarterState = hasQuarterState;
    }
    public State getSoldOutState() {
        return soldOutState;
    }
    public void setSoldOutState(State soldOutState) {
        this.soldOutState = soldOutState;
    }
    public State getSoldState() {
        return soldState;
    }
    public void setSoldState(State soldState) {
        this.soldState = soldState;
    }
    public State getState() {
        return state;
    }
    public void setCount(int count) {
        this.count = count;
    }

简单的实现某一个状态对象

/**
 * 状态实现类
 * @author Dougest 2017年7月17日    上午12:11:16
 *
 */
public class HasQuarterState implements State {
    private CompleMachine compleMachine;
    
    public HasQuarterState(CompleMachine compleMachine) {
        this.compleMachine = compleMachine;
    }
    
    
    @Override
    public void insertQuarter() {
        System.out.println("");
    }
    @Override
    public void ejectQuarter() {
        System.out.println("");
    }
    @Override
    public void turnCrank() {
        System.out.println("");
    }
    @Override
    public void dispense() {
        compleMachine.releaseBall();
        if(compleMachine.getCount() > 0)
            compleMachine.setState(compleMachine.getHasQuarterState());
        else 
            compleMachine.setState(compleMachine.getSoldOutState());
    }