Java 狀態模式

場景：

        一業務系統 報表的報送流程，狀態有 未報送、已報送、審覈通過 和 審覈不通過退回 狀態

定義：

    當一個對象的內在狀態改變時允許改變其行爲，這個對象看起來像是改變了其類。

狀態模式：

示例：

  接口類：

public interface  WaterState {

    public void state();

}

  水凝固狀態類：

public  class FreezeState implements WaterState {

    public void state(){
        System.out.println("Water freezing");
    }
}

  水蒸發類：

public class EvaporateState implements WaterState {

    public void state(){
        System.out.println("Water evaporating");
    }

}

容器類，對應模式中的Context類：

public class Water implements WaterState {

    private WaterState waterState;

    public WaterState getWaterState() {
        return waterState;
    }

    public void setWaterState(WaterState waterState) {
        this.waterState = waterState;
    }

    @Override
    public void state() {
        System.out.println("Water start changed ...");
        waterState.state();
    }
}

測試類：

public class WaterMain {
    public static void main(String args[]) {
        Water water = new Water();
        WaterState waterState = new EvaporateState();
        water.setWaterState(waterState);
        water.state();
    }
}

結果：

Water start changed ...
Water evaporating