Java Switch statement going straight to default using arrays

Question

My switch statement coresponds to an array. The only values in the array are 1-6. I am sure of that. But for some reason the default value is always selected no mater what the value in the array is. Can someone tell me why this is happening?

The variables in the switch statement declared.

   //declares arrays
       int[] vehicle= new int[18];
       int[] gate =  new int[18];
       int index = 0;

    //stores the numbers from the dat files into the arrays

    while(inFile.hasNext()){
        vehicle[index] = inFile.nextInt();
        gate[index] = inFile.nextInt();
        index++;
    }

the switch statement

for( int i = 0; i<vehicle.length; i++){

        switch(vehicle[i]){
            case 1: carType[i] = "Compact Car";
                    break;
            case 2: carType[i] = "Small Car";
                    break;
            case 3: carType[i] = "Mid Size Car";
                    break;
            case 4: carType[i] = "Full Size Car";
                    break;
            case 5: carType[i] = "Truck";
                    break;
            case 6: carType[i] = "16 Wheeler";
                    break;
            default: carType[i] = "Invalid Vehicle Type";
                    break;
                }
            }

EDIT FULL CODE

Object CarCharge class

public class CarChargeAP
{
// instance variables - replace the example below with your own
private int[] vehicle = new int[18];
private int[] gateNumber = new int[18];
private double[] factor = new double[18];
private double[] toll = new double[18]; 
private String[] carType = new String[18];
private double[] cost= new double[18];

/**
 * Constructor for objects of class CarChargeAP
 * pre:none
 * post:variables initialized
 */
public CarChargeAP(int[] vt, int[] gn)
{
    // initialise instance variables
    vt=vehicle;
    gateNumber = gn;

}

/**
 * CarType
 * finds the car types of the vehicles and stores it in an array
 * pre: vehicle arrat initializes
 * post: car type array sorted
 */
public void carType()
{

    for( int i = 0; i<vehicle.length; i++){

        switch(vehicle[i]){
            case 1: carType[i] = "Compact Car";
                    break;
            case 2: carType[i] = "Small Car";
                    break;
            case 3: carType[i] = "Mid Size Car";
                    break;
            case 4: carType[i] = "Full Size Car";
                    break;
            case 5: carType[i] = "Truck";
                    break;
            case 6: carType[i] = "16 Wheeler";
                    break;
            default: carType[i] = "Invalid Vehicle Type";
                    break;
                }
            }


}

/**
 * Toll
 * finds the toll of each of the gates and stores it into an array
 * pre: gateNumber initialized
 * post: toll numbers stored
 */
public void toll(){
    for(int index = 0; index< gateNumber.length; index++){
        switch(gateNumber[index]){
            case 1: toll[index] = 1.35;
                    break;
            case 2: toll[index] = 2.00;
                    break;
            case 3: toll[index] = 2.50;
                    break;
            case 4: toll[index] = 3.25;
                    break;
            case 5: toll[index] = 4.10;
                    break;
            case 6: toll[index] = 4.80;
                    break;
            case 7: toll[index] = 5.50;
                    break;  
            case 8: toll[index] = 6.00;
                    break;
            default: toll[index] = 0;
                    break;
        }
    }

    }


 /**
  * factor
  * finds the factor of the coresponding vehicle type and stores it into array
  * pre: vehicle type initialized
  * post: factor numbers stored
  */
 public void factor()
 {
   for( int i = 0; i<vehicle.length; i++){

        switch(vehicle[i]){
            case 1: factor[i] = 1.0;
                    break;
            case 2: factor[i] = 1.3;
                    break;
            case 3: factor[i] = 1.6;
                    break;
            case 4: factor[i] = 2.0;
                    break;
            case 5: factor[i] = 2.4;
                    break;
            case 6: factor[i] = 2.7;
                    break;
            default: factor[i] = 0;
                    break;
                }
            }  
 }



 /**
  * Cost
  * finds the cost of the fee highway
  * pre: factor, toll, and vehicle initialized
  * post: cost numbers stored
  */
public void cost()
{
    for(int i = 0; i<vehicle.length; i++){
        cost[i] = (factor[i] * toll[i]);
    }
}


/*************************************************
 * Getters
 *************************************************/
/**
 * getCarType
 * getter for car type depending on index
 * pre: cartype initialized
 * post: carType returned
 */
public String getCarType(int i){
    return carType[i];
}

/**
 * getVehicle
 *getter for vehicle 
 *Pre: vehicle initialized
 *post: vehicle returned
 */
public int getVehicle(int i){
    return vehicle[i];
}

/**
 *getGateNumber
 *getter for gate number 
 *Pre: gatNumber initialized
 *post: gate number returned
 */
public int getGateNumber(int i ){
    return gateNumber[i];
}


/**
 * getToll
 * getter for toll
 * pre:toll initialized
 * post: toll returned
 */
public double getToll(int i){
    return toll[i];
}

/**
 * getFactor
 * getter for gactor
 * pre: factor initialized
 * post: factor is returned
 */
public double getFactor(int i){
    return factor[i];
}

/**
 * getCost
 * getter for cost
 * pre: cost initialized
 * post: cost returnded
 */
public double getCost(int i){
    return cost[i];
}

/************************************
 * Setters
 **************************************/

 /**
 * setCarType
 * setter for car type depending on index
 * pre: cartype initialized
 * post: carType set
 */
public void setCarType(int i, String str){
    carType[i] = str;
}

/**
 * setVehicle
 *setter for vehicle 
 *Pre: vehicle initialized
 *post: vehicle set
 */
public void setVehicle(int i, int set){
    vehicle[i] = set;
}

/**
 *setGateNumber
 *seetter for gate number 
 *Pre: gatNumber initialized
 *post: gate number set
 */
public void setGateNumber(int i, int set ){
    gateNumber[i] = set;
}


/**
 * setToll
 * setter for toll
 * pre:toll initialized
 * post: toll set
 */
public void setToll(int i, double set){
    toll[i] = set;
}

/**
 * setFactor
 * setter for gactor
 * pre: factor initialized
 * post: factor is set
 */
public void setFactor(int i, double set){
    factor[i] = set;
}

/**
 * setCost
 * setter for cost
 * pre: cost initialized
 * post: cost set
 */
public void setCost(int i,double set){
    cost[i] = set;
}
}

Tester Class

import java.util.Scanner;
import java.io.*;
public class ChargeTesterAlyiahP
{
public static void main(String[] args){
    //sets up scanner 
    Scanner inFile = null;
    try
    { 
        inFile = new Scanner(new File("prog435a.dat")); 
    }   
    catch(FileNotFoundException e) 
    { 
        System.out.println("File not found!!"); 
        System.exit(0); 
    } 

    //declares arrays
    int[] vehicle= new int[18];
    int[] gate =  new int[18];
    int index = 0;

    //stores the numbers from the dat files into the arrays

    while(inFile.hasNext()){
        vehicle[index] = inFile.nextInt();
        gate[index] = inFile.nextInt();
        index++;
    }

    //creating a carcharge object
    CarChargeAP object = new CarChargeAP(vehicle, gate);

    //calling upon other class to find the values
    object.carType();
    object.toll();
    object.factor();
    object.cost();

    System.out.printf("%5s %5s %5s $5s","Car Type", "Base Toll", "Factor", "Cost");
    for(int i = 0; i<vehicle.length; i++){

        System.out.printf("\n%5s $%5s %5s $%5s",object.getCarType(i), object.getToll(i), object.getFactor(i), object.getCost(i));

    }

}


}

Easy. Your array is full of 0. System.out.println(Arrays.toString(vehicle)); — Elliott Frisch
– Elliott Frisch, Commented Feb 25, 2018 at 21:47
I'm not convinced that, at any point in time, any value in your carType array is not zero. — Makoto
– Makoto, Commented Feb 25, 2018 at 21:47
@ElliottFrisch Why is it 0? I make it equal to the next int on my file and the file does not have any 0's — Issame
– Issame, Commented Feb 25, 2018 at 21:49
int[] vehicle= new int[18]; fills it with 0. You assumed your file reading code worked. Based on your problem description, I think you are mistaken. Ergo, the array is filled with 18 zeros. — Elliott Frisch
– Elliott Frisch, Commented Feb 25, 2018 at 21:52
@ElliottFrisch Here's the thing. I have another switch statement for the array gate which works perfectly fine. Meaning the the file reading worked for that variable. Do you see any reason why it doesn't work for the Vehicle variable? Very stuck here — Issame
– Issame, Commented Feb 25, 2018 at 21:55

Maarten Bodewes · Accepted Answer · 2018-02-25 22:20:25Z

1

Your constructor is incorrect:

public CarChargeAP(int[] vt, int[] gn)
{
    // initialise instance variables
    vt=vehicle;
    gateNumber = gn;

}

here vehicle, your field is assigned to vt, which is an input parameter. This would have caused an error if you had not assigned an unused, empty array to the vehicle field:

private int[] vehicle = new int[18];

However, this should not be resolved by just changing the order of the variable assignment: vehicle = vt. Instead you should be copying the values from arrays:

System.arraycopy(vt, 0, vehicle, 0, vehicle.length);

That way changes to the vt aren't reflected in the class, i.e. this should not be possible:

CarChangeAP ap = new CarChangeAP(vt, gn);
// changes the field within ap
vt[0] = -1;

as it violates the encapsulation of the data within the fields of the class instance. Data within the class should only be updated using the methods of the class. Now the field is private but the contents can still be changed, as arrays in Java are always mutable.

answered Feb 25, 2018 at 22:20

Maarten Bodewes

94.6k15 gold badges169 silver badges289 bronze badges

Sign up to request clarification or add additional context in comments.

1 Comment

Maarten Bodewes Over a year ago

In the constructor you should also validate that the size & contents of the arrays is correct. This is called fail fast where you make sure that your class instances do not have invalid state (before your code fails later on because of the invalid state). That's probably for another lesson though.

Ezell Buoee · Accepted Answer · 2018-02-25 21:53:48Z

i don't what's happening but this works for me

        int[] vehicle = new int[6];
    String[] carType = new String[6];
    for (int a = 0; a < vehicle.length; a++) {
        vehicle[a] = a + 1;
    }
    for (int i = 0; i < vehicle.length; i++) {

        switch (vehicle[i]) {
            case 1:
                carType[i] = "Compact Car";
                break;
            case 2:
                carType[i] = "Small Car";
                break;
            case 3:
                carType[i] = "Mid Size Car";
                break;
            case 4:
                carType[i] = "Full Size Car";
                break;
            case 5:
                carType[i] = "Truck";
                break;
            case 6:
                carType[i] = "16 Wheeler";
                break;
            default:
                carType[i] = "Invalid Vehicle Type";
                break;
        }
    }
    for (int a = 0; a < carType.length; a++) {
        System.out.println(carType[a]);
    }

which means something else is happening to the file you are reading from, can you post your full code including the file reader

Collectives™ on Stack Overflow

Java Switch statement going straight to default using arrays

2 Answers 2

1 Comment

Comments

Your Answer

Hot Network Questions

Collectives™ on Stack Overflow

2 Answers 2

1 Comment

Comments

Your Answer

Sign up or log in

Post as a guest

Related