如何返回在 switch 语句中找到的值 Java

Question

How would I return the values that I found in this switch statement to the rest of the class for use (I want to use oneTotal, twoTotal, etc. out side of that switch statement)? Here is the code for the switch statement:

        switch(itemNo){
        case 1:
            double oneTotal = 2.98 * userQuantity;
            return oneTotal;
        case 2:
            double twoTotal = 4.50 * userQuantity;
            return twoTotal;
        case 3:
            double threeTotal = 9.98 * userQuantity;
            return threeTotal;
        case 4:
            double fourTotal = 4.49 * userQuantity;
            return fourTotal;
        case 5:
            double fiveTotal = 6.87 * userQuantity;
            return fiveTotal;
        }

Out side of the switch statement I want the fiveTotal's to be added up once the user's stops using the switch statement (I have it in a while loop), and then want the five totals to be returned to be used in the main method of the class (the switch statement is in its own double, non void class so it can return values).

Answer 1

Just try defining a variable called result of double type before switch statement like:

double result = 0.;
switch(itemNo){
    case 1: 
        result = 2.98 * userQuantity; 
        break;
     ....
}
return result;

Answer 2

The method must only contain the necessary code to do its work. The consumers of the method must worry about how to work with the data.

For your case, your method containing this switch must only care about returning the proper value based on the parameter(s), and the clients of the method eg public static void main(String[] args) must evaluate what to do with the results from executing this method.

Here's how this may work for your case:

public static double yourMethod(int itemNo) {
    double result = 0;
    switch(itemNo) {
        case 1:
            result = 2.98 * userQuantity;
            break;
        case 2:
            result = 4.50 * userQuantity;
            break;
        case 3:
            result = 9.98 * userQuantity;
            break;
        case 4:
            result = 4.49 * userQuantity;
            break;
        case 5:
            result = 6.87 * userQuantity;
            break;
    }
    return result;
}

public static void main(String[] args) {
    //some code...
    double grandTotal = 0;

    //probably this may be in a loop or something similar
    int itemNo = ...;
    //this method is consumer/client of yourMethod, directly noted by line below
    double someValue = yourMethod(itemNo);
    grandTotal += someValue;

    //more code...
    //do something with the result e.g. print it so the user may read it
    System.out.println("Grand total: " + grandTotal);
}

Answer 3

You can create a variable out side the switch statement and is visible for rest of the class to keep track of the return values:

public double sumFives = 0; //global variable
/* some codes */
switch(itemNo){
    case 1:
        double oneTotal = 2.98 * userQuantity;
        return oneTotal;
    case 2:
        double twoTotal = 4.50 * userQuantity;
        return twoTotal;
    case 3:
        double threeTotal = 9.98 * userQuantity;
        return threeTotal;
    case 4:
        double fourTotal = 4.49 * userQuantity;
        return fourTotal;
    case 5:
        double fiveTotal = 6.87 * userQuantity;
        sumFives += fiveTotal;
        return fiveTotal;
    }
}

There, you'll have access to the sum after the switch statement. If you want to track each individual return values, simple use an ArrayList.

Hope this helps :)

Yang

Answer 4

On Java 14, you can use

double total = switch(itemNo){
        case 1 -> 2.98 * userQuantity;
        case 2 -> 4.50 * userQuantity;
        case 3 -> 9.98 * userQuantity;
        case 4 -> 4.49 * userQuantity;
        case 5 -> 6.87 * userQuantity;
        };

Answer 5

    double returnValue;
    switch(itemNo){
    case 1:
        double oneTotal = 2.98 * userQuantity;
        returnValue = oneTotal;
        break;
    case 2:
        double twoTotal = 4.50 * userQuantity;
        returnValue = twoTotal;
        break;
    case 3:
        double threeTotal = 9.98 * userQuantity;
        returnValue = threeTotal;
        break;
    case 4:
        double fourTotal = 4.49 * userQuantity;
        returnValue = fourTotal;
        break;
    case 5:
        double fiveTotal = 6.87 * userQuantity;
        returnValue = fiveTotal;
        break;
    }
    return returnValue; 

or

    double factor;
    switch(itemNo){
    case 1:
        factor = 2.98;
        break;
    case 2:
        factor = 4.50;
        break;
    case 3:
        factor = 9.98;
        break;
    case 4:
        factor = 4.49;
        break;
    case 5:
        factor = 6.87;
        break;
    }
    return factor * userQuantity;

And don't forget the default branch. Throw an exception at least.

or

double[] myItemValues= {2.98, 4.5, 9.98, 4.49, 6.87};
return myItemValue[itemNo];

Answer 6

Define a variable on top of switch statement so that it is visible for switch scope. then assign your value to that variable in each case. Then as last line return your assigned variable.

Answer 7

The following should work:

    double total;
    switch(itemNo){
    case 1:
        total = 2.98 * userQuantity;
        break;
    case 2:
        total = 4.50 * userQuantity;
        break;
    case 3:
        total = 9.98 * userQuantity;
        break;
    case 4:
        total = 4.49 * userQuantity;
        break;
    case 5:
        total = 6.87 * userQuantity;
        break;
    default:
        throw new IllegalArgumentException("selected: " + itemNo);
    }
    return total;

Answer 8

double value = 0.0;
switch(itemNo){
     case 1:
        double oneTotal = 2.98 * userQuantity;
        value = oneTotal;
        break;
     case 2:
        double twoTotal = 4.50 * userQuantity;
        value = twoTotal;
        break;
     case 3:
        double threeTotal = 9.98 * userQuantity;
        value = threeTotal;
        break;
      case 4:
        double fourTotal = 4.49 * userQuantity;
        value = fourTotal;
      case 5:
        double fiveTotal = 6.87 * userQuantity;
        value = fiveTotal;
        break;
          }
return value;

Answer 9

I'm not sure the implementation you are looking to use this in....however it seems like you are on the right track.

Simply wrap your switch statement into a method

...
double total = 0;
while(loopControl){
total += getSwitch(switchValue);
}
....

public double getSwitch(switchValue){
double returnValue = 0;
switch(switchValue){
case 1:
    returnvalue = *your formula*;
    break;
....
}
return returnValue;
}

edit for passing in argument for whatever your switch value will be apologies...

Answer 10

There are two ways you can go about this depending on what you want to do. First, If you want to just keep adding the sum, you can define a variable outside the function and keep incrementing it.

Eg:

double result = 0.0;
while(*your condition*){
    //Take itemNo from user
    switch(itemNo){
        case 1: 
           result += 2.98 * userQuantity; //The += ensures you are cumulating
           break;
        ....
    }
}
return result;

Or, If you want to have those values distinct then you can keep an array[5]

double result[5]={0.0, 0.0, 0.0, 0.0, 0.0};
switch(itemNo){
case 1:
    result[0] = 2.98 * userQuantity;
    break;
case 2:
    result[1] = 4.50 * userQuantity;
    break;
case 3:
    result[2] = 9.98 * userQuantity;
    break;
case 4:
    result[3] = 4.49 * userQuantity;
    break;
case 5:
    result[4] = 6.87 * userQuantity;
    break;
}
return result; 

This was you will can have explicit knowledge outside your switch-case of what the user entered and do any manipulation with the data.

Answer 11

This can also be written as mentioned below,

switch(itemNo){
        case 1:
            return 2.98 * userQuantity;
        case 2:
            return 4.50 * userQuantity;
        case 3:
            return 9.98 * userQuantity;
        case 4:
            return 4.49 * userQuantity;
        case 5:
            return 6.87 * userQuantity;
        }
        return 0; //default value