数组索引超出范围

Question

这就是我要做的事情:我正在从命令行读取文件.该文件包含一个数据列表,下面这段是它的样子.我遇到的问题是if语句.

import java.util.*;
import java.io.*;

public class VehicleTest {
    public static void main(String[] args) throws FileNotFoundException {
        String vehicle = "vehicle";
        String car = "car";
        String americanCar = "american car";
        String foreignCar = "foreign car";
        String truck = "truck";
        String bicycle = "bicycle";

        File file = new File(args[0]);
        Scanner input = new Scanner(file);

        String[] autos = new String[100];
        ArrayList allVehicles = new ArrayList();


        for (int i = 0; i < autos.length; i++) {
            autos[i] = input.nextLine();
        }

        int j = 0;
        int i = 0;

        while (i++ < autos.length) {
            if (vehicle.equalsIgnoreCase(autos[j++])) {
                Vehicle v = new Vehicle();
                v.setOwnerName(autos[j]);
                allVehicles.add(v);
            }else if(car.equalsIgnoreCase(autos[j++])){
                Car c = new Car();
                c.setOwnerName(autos[j]);
                allVehicles.add(c);
            }
        }

        for(Object a: allVehicles){
            System.out.println(a);
        }
    }
}

在伪代码中,这将是:

while i is less than the length of the string  array  
 if you see the word vehicle create a new vehicle object and add it to the arrayList.  
 if you see the word car create a new car object and add it to the arrayList.  
.....

问题是我使用我正在使用的代码得到一个arrayOutOfBounds异常.

我知道j ++是错的,但是我应该如何遍历字符串数组以便我可以读取每一行并创建适当的对象？我不知道该怎么做.我需要一些帮助.

foreign car  
aMarioy  
Mario's house  
(777) 777-7777  
gmario@mario.com  
false  
black  
Italy  
4415.91  

truck  
aDougy  
Doug's house  
(123) 456-7890  
hdoug@doug.com  
30  
61234.56  
8/10/2003  

vehicle  
aRobby  
Rob's house  
(987) 654-3210  
irob@rob.com  

bicycle  
bTommy  
Tom's house  
(246) 810-1214  
jtom@tom.com  
7  

truck  
bGeorge  
George's house  
(666) 666-6666  
kgeorge@george.com  
25  
51234.56  
12/4/2004  

vehicle  
bTim  
Tim's house  
(111) 111-1111  
tim@tim.com  

bicycle  
bJim  
Jim's house  
(555) 555-5555  
Ajim@jim.com  
5  

american car  
bJohn  
John's house  
(888) 888-8888  
Bjohn@john.com  
true  
green  
false  
true  

car  
cKen  
Ken's house  
(999) 999-9999  
Cken@ken.com  
false  
orange  

foreign car  
cMario  
Mario's house  
(777) 777-7777  
Dmario@mario.com  
false  
black  
Italy  
4415.91  


american car  
gSam  
Sam's house  
(333) 333-3333  
Hsam@sam.com  
false  
blue  
true  
false  

Answer 1

一些问题:

• 你在两个"if"测试中增加了j.我没有检查确定(这是相当复杂的代码,说实话)但如果你确定你只是在找到匹配时增加j,那将有所帮助.
• 您的测试i基本上意味着它将尝试读取与文件中的行一样多的车辆,而不是在您到达文件末尾时停止.基本上你不需要i这里.

这是一个改变版本:

    while (j < autos.length) {
        if (vehicle.equalsIgnoreCase(autos[j])) {
            j++;
            Vehicle v = new Vehicle();
            v.setOwnerName(autos[j++]);
            allVehicles.add(v);
        } else if(car.equalsIgnoreCase(autos[j])){
            j++;
            Car c = new Car();
            c.setOwnerName(autos[j++]);
            allVehicles.add(c);
        }
    }

虽然提取类型会稍微清晰一点 - 然后你可以单独进行比较:

    while (j < autos.length) {
        String type = autos[j++];
        if (vehicle.equalsIgnoreCase(type)) {
            Vehicle v = new Vehicle();
            v.setOwnerName(autos[j++]);
            allVehicles.add(v);
        } else if(car.equalsIgnoreCase(type)){
            Car c = new Car();
            c.setOwnerName(autos[j++]);
            allVehicles.add(c);
        }
    }

它仍然不是我怎么做的,但它更接近......

我的下一步是更合适地使用扫描仪:

while (scanner.hasNext()) {
    String type = scanner.nextLine();
    if (type.equalsIgnoreCase("vehicle")) {
        allVehicles.add(new Vehicle(scanner));
    } else if (type.equalsIgnoreCase("car")) {
        allVehicles.add(new Car(scanner));
    }
    // ...
}

然后使Vehicle,Car等的构造函数直接从扫描程序进行解析.

下一步是将构造与迭代分开.介绍一种新方法:

// Use a base type in real code
private static Object parseNextVehicle(Scanner scanner) {
    String type = scanner.nextLine();
    if (type.equalsIgnoreCase("vehicle")) {
        return new Vehicle(scanner);
    } else if (type.equalsIgnoreCase("car")) {
        return new Car(scanner);
    }
    // ... throw an exception indicating an unknown vehicle type
}

// ... and then in the main method, use it like this:
while (scanner.hasNextLine()) {
    allVehicles.add(parseNextVehicle(scanner));
}