我的开关语句对应于数组。数组中唯一的值是1-6。我确定这一点。但是由于某种原因，始终没有选择默认值。数组中的值是什么。有人可以告诉我为什么会发生这种情况吗？
已声明的切换语句中的变量已声明。
//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++;
}
开关语句
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;
}
}
编辑完整代码
对象carcharge类
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;
}
}
测试仪类
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));
}
}
}
您的构造函数不正确：
public CarChargeAP(int[] vt, int[] gn)
{
// initialise instance variables
vt=vehicle;
gateNumber = gn;
}
在此vehicle，您的字段分配给vt，这是输入参数。如果您未分配未使用的，空数组到vehicle字段：
private int[] vehicle = new int[18];
但是，不应仅通过更改变量分配的顺序来解决这：vehicle = vt。相反，您应该从数组中复制值：
System.arraycopy(vt, 0, vehicle, 0, vehicle.length);
这样，将变成vt的方式不会反映在班级中，即不可能：
CarChangeAP ap = new CarChangeAP(vt, gn);
// changes the field within ap
vt[0] = -1;
因为它违反了类实例字段中数据的封装。仅应使用类的方法来更新类中的数据。现在该字段是private，但内容仍然可以更改，因为Java中的数组是始终可变的。
我不发生什么，但这对我有用
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]);
}
这意味着您正在阅读的文件中正在发生其他事情，您可以发布完整代码，包括文件读取器