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



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


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

Maarten Bodewes · Accepted Answer

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.

Java Switch statement going straight to default using arrays

Answers (2)

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