Question

如果它似乎无关紧要，即值是一个参数而且函数不直接在调用对象实例上运行，那么＆＃34;引擎盖下是什么？调用Class.function（）和Object.function（）？

之间的区别

这可以通过一个错综复杂的例子来说明：

public String getImsiSIM1() {
    return imsiSIM1;
}
public String getImsiSIM2() {
    return imsiSIM2;
}
public boolean isSIM1Ready() {
    return isSIM1Ready;
}
public boolean isSIM2Ready() {
    return isSIM2Ready;
}

/*public static void setSIM2Ready(boolean isSIM2Ready) {
    TelephonyInfo.isSIM2Ready = isSIM2Ready;
}*/

public boolean isDualSIM() {
    return imsiSIM2 != null;
}


public  String getNetworkOperator(){
    return networkOperatorOne ;
}
public String getNetworkOperatorDual(){
    return  networkOperatorDual ;

}

private TelephonyInfo() {
}

public static TelephonyInfo getInstance(Context context){

    if(telephonyInfo == null) {

        telephonyInfo = new TelephonyInfo();

        TelephonyManager telephonyManager = ((TelephonyManager) context.getSystemService(Context.TELEPHONY_SERVICE));

        telephonyInfo.imsiSIM1 = telephonyManager.getDeviceId();;
        telephonyInfo.imsiSIM2 = null;

        telephonyInfo.networkOperatorOne =telephonyManager.getNetworkOperator();
        telephonyInfo.networkOperatorDual = null ;

        try {
            telephonyInfo.imsiSIM1 = getDeviceIdBySlot(context, "getDeviceIdGemini", 0);
            telephonyInfo.imsiSIM2 = getDeviceIdBySlot(context, "getDeviceIdGemini", 1);
            telephonyInfo.networkOperatorOne = getCarrierName(context,"getCarrierName",0);
            telephonyInfo.networkOperatorDual = getCarrierName(context,"getCarrierName",1);

        } catch (GeminiMethodNotFoundException e) {
            e.printStackTrace();

            try {
                telephonyInfo.imsiSIM1 = getDeviceIdBySlot(context, "getDeviceId", 0);
                telephonyInfo.imsiSIM2 = getDeviceIdBySlot(context, "getDeviceId", 1);
                telephonyInfo.networkOperatorOne = getCarrierName(context,"getCarrierName",0);
                telephonyInfo.networkOperatorDual = getCarrierName(context,"getCarrierName",1);
            } catch (GeminiMethodNotFoundException e1) {
                //Call here for next manufacturer's predicted method name if you wish
                e1.printStackTrace();
            }
        }

        telephonyInfo.isSIM1Ready = telephonyManager.getSimState() == TelephonyManager.SIM_STATE_READY;
        telephonyInfo.isSIM2Ready = false;

        try {
            telephonyInfo.isSIM1Ready = getSIMStateBySlot(context, "getSimStateGemini", 0);
            telephonyInfo.isSIM2Ready = getSIMStateBySlot(context, "getSimStateGemini", 1);
        } catch (GeminiMethodNotFoundException e) {

            e.printStackTrace();

            try {
                telephonyInfo.isSIM1Ready = getSIMStateBySlot(context, "getSimState", 0);
                telephonyInfo.isSIM2Ready = getSIMStateBySlot(context, "getSimState", 1);
            } catch (GeminiMethodNotFoundException e1) {
                //Call here for next manufacturer's predicted method name if you wish
                e1.printStackTrace();
            }
        }

    }

    return telephonyInfo;
}

private static String getDeviceIdBySlot(Context context, String predictedMethodName, int slotID) throws GeminiMethodNotFoundException {

    String imsi = null;

    TelephonyManager telephony = (TelephonyManager) context.getSystemService(Context.TELEPHONY_SERVICE);

    try{

        Class<?> telephonyClass = Class.forName(telephony.getClass().getName());

        Class<?>[] parameter = new Class[1];
        parameter[0] = int.class;
        Method getSimID = telephonyClass.getMethod(predictedMethodName, parameter);

        Object[] obParameter = new Object[1];
        obParameter[0] = slotID;
        Object ob_phone = getSimID.invoke(telephony, obParameter);

        if(ob_phone != null){
            imsi = ob_phone.toString();

        }
    } catch (Exception e) {
        e.printStackTrace();
        throw new GeminiMethodNotFoundException(predictedMethodName);
    }

    return imsi;
}

private static  boolean getSIMStateBySlot(Context context, String predictedMethodName, int slotID) throws GeminiMethodNotFoundException {

    boolean isReady = false;

    TelephonyManager telephony = (TelephonyManager) context.getSystemService(Context.TELEPHONY_SERVICE);

    try{

        Class<?> telephonyClass = Class.forName(telephony.getClass().getName());

        Class<?>[] parameter = new Class[1];
        parameter[0] = int.class;
        Method getSimStateGemini = telephonyClass.getMethod(predictedMethodName, parameter);

        Object[] obParameter = new Object[1];
        obParameter[0] = slotID;
        Object ob_phone = getSimStateGemini.invoke(telephony, obParameter);

        if(ob_phone != null){
            int simState = Integer.parseInt(ob_phone.toString());
            if(simState == TelephonyManager.SIM_STATE_READY){
                isReady = true;
            }
        }
    } catch (Exception e) {
        e.printStackTrace();
        throw new GeminiMethodNotFoundException(predictedMethodName);
    }

    return isReady;
}

private static String getCarrierName(Context context, String predictedMethodName, int slotID) throws GeminiMethodNotFoundException {

    String carrier = null;

    TelephonyManager telephony = (TelephonyManager) context.getSystemService(Context.TELEPHONY_SERVICE);

    try{

        Class<?> telephonyClass = Class.forName(telephony.getClass().getName());

        Class<?>[] parameter = new Class[1];
        parameter[0] = int.class;
        Method sim = telephonyClass.getMethod(predictedMethodName, parameter);

        Object[] obParameter = new Object[1];
        obParameter[0] = slotID;
        Object ob_phone = sim.invoke(telephony, obParameter);

        if(ob_phone != null){
            carrier = ob_phone.toString();
            if(carrier .equals(TelephonyManager.SIM_STATE_READY)) {
                Log.d("Services","servicessss"+carrier);
                 ;
            }

        }
    } catch (Exception e) {
        e.printStackTrace();
        throw new GeminiMethodNotFoundException(predictedMethodName);
    }

    return carrier;
}


private static class GeminiMethodNotFoundException extends Exception {

    private static final long serialVersionUID = -996812356902545308L;

    public GeminiMethodNotFoundException(String info) {
        super(info);
    }
}
}

VS

Character c = new Character();
boolean b = c.isDigit(c);

如果只重复使用Character而不是一堆不同的实例名称，我可以看到硬编码变量更易于更改（查找/替换）的情况。最重要的是：最受欢迎的最佳做法是什么？

Answer 1

对于静态方法，内部c.isDigit(c)被视为Character.isDigit(c);

在使用引用变量调用静态方法的情况下，编译器只需用类名替换引用变量。

Answer 2

完全没有区别。这是Java语法的一个怪癖，您可以通过实例引用调用static方法。无论您是调用Character.isDigit还是c.isDigit，编译器都会发出相同的字节码，甚至不关心运行时c是否为null（因为c在运行时不参与调用 - 因为字节码正在执行Character.isDigit）。

Java：Class.function（）和Object.function（）之间的区别

2 个答案: