java - 为什么这是一个遥不可及的声明？

Question

在此代码的底部，我收到“无法访问的语句”错误。我尝试了一些事情，但无法弄清楚为什么会这样。错误在代码的底部（我已经用//评论了错误所在的位置）请帮助我指出正确的方向，我很难过！

/**
* Describes a certain model.
* 
* @author (Joshua Baker) 
* @version (1.0)
*/
public class Model
{
public static final int IN_PER_FOOT = 12;
public static final int BASE_RATE = 60;
public static final int TALL_INCHES = 67;
public static final double THIN_POUNDS = 140.0;
public static final int TALL_THIN_BONUS = 5;
public static final int TRAVEL_BONUS = 4;
public static final int SMOKER_DEDUCTION = 10;

private String firstName;
private String lastName;
private int heightInInches;
private double weightInPounds;
private boolean travel;
private boolean smokes;
private String newHeight;
private int perHourRate;

/**
 * Default constructor
 */
public Model()
{
    setFirstName ("");
    setLastName  ("");
    setHeightInInches  (0);
    setWeightInPounds  (0.0);
    setTravel  (false);
    setSmokes  (false);
}

/**
 * 
 */
public Model (String whatIsFirstName, String whatIsLastName, int whatIsHeight, double whatIsWeight,
boolean canTravel, boolean smoker)
{
    setFirstName  (whatIsFirstName);
    setLastName  (whatIsLastName);
    setHeightInInches  (whatIsHeight);
    setWeightInPounds  (whatIsWeight);
    setTravel  (canTravel);
    setSmokes  (smoker);
}

/**
 *@return first name
 */
public String getFirstName()
{
    return firstName;
}

/**
 *@return last name
 */
public String getLastName()
{
    return lastName;
}

/**
 *@return height in inches
 */
public int getHeightInInches()
{
    return heightInInches;
}

/**
 *@return the converted height 
 */
public String getNewHeight()
{
    return newHeight;
}

/**
 *@return weight in pounds
 */
public double getWeightInPounds()
{
    return weightInPounds;
}

/**
 *@return models pay per hour rate
 */
public int getPerHourRate()
{
    return perHourRate;
}


/**
 *@return travel
 */
public boolean getTravel()
{
    return travel;
}

/**
 *@return smokes
 */
public boolean getSmokes()
{
    return smokes;
}

/**
 * models first name
 */
public void setFirstName(String whatIsFirstName)
{
    firstName = whatIsFirstName;
}

 /**
 * models last name
 */
public void setLastName(String whatIsLastName)
{
    lastName = whatIsLastName;
}

 /**
 * models height in inches
 */
public void setHeightInInches(int whatIsHeight)
{
    if (whatIsHeight >0){
    heightInInches = whatIsHeight;
    }

}

 /**
 * models weight in pounds
 */
public void setWeightInPounds(double whatIsWeight)
{
    if (whatIsWeight >0){
    weightInPounds = whatIsWeight;
    }
}

 /**
 * can model travel
 */
public void setTravel(boolean canTravel)
{
    travel = canTravel;
}

 /**
 * does model smoke
 */
public void setSmokes(boolean smoker)
{
    smokes = smoker;
}

/**
 * Converts to feet and inches
 */
public String convertheightToFeetInches() 
{
int leftOver = (heightInInches %= IN_PER_FOOT);
int newHeight = (heightInInches % IN_PER_FOOT);
return newHeight + "Foot" + leftOver + "Inches";
}

/**
 * 
 */
public int calculatePayPerHour(){
    if (heightInInches  >= TALL_INCHES && (weightInPounds <= THIN_POUNDS)) {
        perHourRate = BASE_RATE + TALL_THIN_BONUS;
        return perHourRate;
    }
    else
    {
        perHourRate = BASE_RATE;
        return perHourRate;
    }

    if (travel)  {          //unreachable statement


        perHourRate = BASE_RATE + TRAVEL_BONUS;   
        return perHourRate;
    }
    else
    {
        perHourRate = BASE_RATE;
        return perHourRate;

    }

    if (smokes) {             //unreachable statement
        perHourRate = BASE_RATE - SMOKER_DEDUCTION;
        return perHourRate;
    }

    else {}

    }






/**
 * Displays details
 */
public  void displayInfo()
{
    System.out.print("Name : " + getFirstName() + " ");
    System.out.println(getLastName());
    System.out.println("Height : " + getNewHeight() + "inches");
    System.out.println("Weight : " + getWeightInPounds() + "pounds");
    System.out.print("Travel : " + getTravel() + " " );
    System.out.print("Smokes : " + getSmokes() );
    System.out.println("Hourly rate : " + getPerHourRate() );
}

}

Answer 1

那是因为您的程序将从您的第一个if block或相应的else块返回：-

if (heightInInches  >= TALL_INCHES && (weightInPounds <= THIN_POUNDS)) {
    perHourRate = BASE_RATE + TALL_THIN_BONUS;
    return perHourRate;
}
else
{
    perHourRate = BASE_RATE;
    return perHourRate;
}
System.out.println("This will never get printed. And will show compiler error");

因此，将执行两个 return 语句中的任何一个。因此，任何进一步的代码都无法访问。

---

似乎您希望获得所有 的累积总和service rates以获得最终的perHourRate，为此，您可以return statement从每个if-else块中删除 。然后对于if-else第一个块之后的所有块，而不是分配current priceto perHourRate，做一个compound addition +=.

此外，由于您正在处理实例字段 - perHourRate，因此您根本不需要返回它。您所做的更改perHourRate可以使用getPerHourRate(). 因此，将返回类型更改为void.

您可以尝试将您的calculatePayPerHour方法更新为以下方法：

public void calculatePayPerHour(){
    if (heightInInches  >= TALL_INCHES && (weightInPounds <= THIN_POUNDS)) {
        perHourRate = BASE_RATE + TALL_THIN_BONUS;  // Initial assignment

    } else {
        perHourRate = BASE_RATE;  // Initial assignment
    }

    /** Rest of the assignment will be compound assignment, since you
        are now updating the `perHourRate` **/

    if (travel)  {      
        perHourRate += TRAVEL_BONUS;   
    } // You don't need an else now. Since BASE_RATE is already added

    if (smokes) {    
        perHourRate -= SMOKER_DEDUCTION;
    }
}

Answer 2

在您的calculatePayPerHour方法中，您有一个 if/else 并且永远不会到达该语句，因为在这两种情况下您都返回一个结果：

if (heightInInches  >= TALL_INCHES && (weightInPounds <= THIN_POUNDS)) {
    perHourRate = BASE_RATE + TALL_THIN_BONUS;
    return perHourRate; // you return in the if
}
else
{
    perHourRate = BASE_RATE;
    return perHourRate; // you return in the else
}

... the execution will never reach here

Answer 3

if (heightInInches  >= TALL_INCHES && (weightInPounds <= THIN_POUNDS)) {
    perHourRate = BASE_RATE + TALL_THIN_BONUS;
    return perHourRate; // <------------
}
else
{
    perHourRate = BASE_RATE;
    return perHourRate;  // <------------
}

无论您的身高或体重如何，这两个返回中的一个都会触发，因此它之后的任何语句都不会被执行。这与下面的代码相同。

if (heightInInches  >= TALL_INCHES && (weightInPounds <= THIN_POUNDS)) {
    perHourRate = BASE_RATE + TALL_THIN_BONUS;
}
else
{
    perHourRate = BASE_RATE;
}

return perHourRate;  
//unreachable

Answer 4

• 在您的方法public int calculatePayPerHour()中，第一个 if else 语句在任何情况下都返回一个值（在 if 和 else 块中）。
• 如果您试运行该程序，您将看到控制流永远不会到达此块下方的语句，因此您的异常。

Answer 5

在代码上方的 if/else 中，您已经有 2 个 return 语句......这意味着它永远不会到达下面的代码......