Java中神秘的运行时错误

Question

我正在编写的一个java程序遇到了一些问题。它旨在分析制表符分隔的文本文件，然后将其存储到数组列表中。我正在尝试使用java程序更改制表符分隔的文本文件的格式。然而，我的代码得到了一个奇怪的运行时错误。以下是我的代码

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

public class Parse
{
    public static void main(String[] args) {
        try{
            Scanner scanner = new Scanner(new File("C:\\Users\\Nelson Liu\\My Documents\\ParsePlanets\\SearchResults.txt"));
            ArrayList < String > list = new ArrayList < String > ();
            scanner.useDelimiter("\t");
            while (scanner.hasNext()) {
                list.add(scanner.next());
            }
            scanner.close();
            String currenttarget = "Mercury";
            String currentfeaturetype = "Albedo Feature";
            String featuretypebeforecomma = "albedo";
            PrintWriter writer = new PrintWriter("jpl-" + currenttarget + "-" + featuretypebeforecomma + ".txt", "UTF-8");
            String classname = "jpl-" + currenttarget + "-" + featuretypebeforecomma;
            int multiplier = 0;
            int j = 0;
            int testingtarget = 0;
            int testingfeature = 0;
            while (multiplier < 15145) {
                testingtarget = (j+2) + (10*multiplier);
                testingfeature = (j + 6) +(10*multiplier);
                if((list.get(testingtarget) == currenttarget) && (list.get(testingfeature) == currentfeaturetype)){
                    writer.print(classname);
                    writer.print("\t");
                    writer.print(list.get((j+2) + (10*multiplier)-1));
                    writer.print("\t");
                    writer.print("CODE");
                    writer.print("\t");
                    writer.print(list.get((j+2) + (10*multiplier)-2));
                    writer.print("\t");
                    writer.print("\n");

                    writer.print(classname);
                    writer.print("\t");
                    writer.print(list.get((j+2) + (10*multiplier)-1));
                    writer.print("\t");
                    writer.print("TARGET");
                    writer.print("\t");
                    writer.print(list.get((j+2) + (10*multiplier)));
                    writer.print("\t");
                    writer.print("\n");

                    writer.print(classname);
                    writer.print("\t");
                    writer.print(list.get((j+2) + (10*multiplier)-1));
                    writer.print("\t");
                    writer.print("DIAMETER");
                    writer.print("\t");
                    writer.print(list.get((j+2) + (10*multiplier)+1));
                    writer.print("\t");
                    writer.print("\n");

                    writer.print(classname);
                    writer.print("\t");
                    writer.print(list.get((j+2) + (10*multiplier)-1));
                    writer.print("\t");
                    writer.print("LATITUDE-LONGITUDE");
                    writer.print("\t");
                    writer.print(list.get((j+2) + (10*multiplier)+5));
                    writer.print(list.get((j+2) + (10*multiplier)+5) + "," + list.get((j+2) + (10*multiplier)+6));
                    writer.print("\t");
                    writer.print("\n");

                    writer.print(classname);
                    writer.print("\t");
                    writer.print(list.get((j+2) + (10*multiplier)-1));
                    writer.print("\t");
                    writer.print("FEATURE-TYPE");
                    writer.print("\t");
                    writer.print(list.get((j+2) + (10*multiplier)+4));
                    writer.print("\t");
                    writer.print("\n");

                    writer.print(classname);
                    writer.print("\t");
                    writer.print(list.get((j+2) + (10*multiplier)-1));
                    writer.print("\t");
                    writer.print("APPROVAL-STATUS");
                    writer.print("\t");
                    writer.print(list.get((j+2) + (10*multiplier)+5));
                    writer.print("\t");
                    writer.print("\n");

                    writer.print(classname);
                    writer.print("\t");
                    writer.print(list.get((j+2) + (10*multiplier)-1));
                    writer.print("\t");
                    writer.print("APPROVAL-DATE");
                    writer.print("\t");
                    writer.print(list.get((j+2) + (10*multiplier)+6));
                    writer.print("\t");
                    writer.print("\n");

                    writer.print(classname);
                    writer.print("\t");
                    writer.print(list.get((j+2) + (10*multiplier)-1));
                    writer.print("\t");
                    writer.print("ORIGIN");
                    writer.print("\t");
                    writer.print(list.get((j+2) + (10*multiplier)+7));
                    writer.print("\t");
                    writer.print("\n");

                }

                multiplier = multiplier +1 ;

            }
        } catch(Exception e){
            System.out.println("error");
        }
    }
}

我取消了第1行到第1行的注释，程序运行得很好，除非出现行乘数=乘数+1；

更奇怪的是，我尝试在IDE中使用调试器，结果主类显示为空。

堆栈跟踪(从注释复制)：

java.lang.IndexOutOfBoundsException: Index: 432, Size: 427 at 
java.util.ArrayList.rangeCheck(ArrayList.java:604) at 
java.util.ArrayList.get(ArrayList.java:382) at Parse.main(Parse.java:28) at    
__SHELL4.run(__SHELL4.java:6) at 
sun.reflect.NativeMethodAccessorImpl.invoke0(Native Method) at 
sun.reflect.NativeMethodAccessorImpl.invoke(NativeMethodAccessorImpl.java:57) at 
sun.reflect.DelegatingMethodAccessorImpl.invoke(DelegatingMethodAccessorImpl.jav‌​a:43) at 
java.lang.reflect.Method.invoke(Method.java:606) at 
bluej.runtime.ExecServer$3.run(ExecServer.java:725) 

提前感谢你的帮助，我真的被卡住了。

Answer 1

试试useDelimiter("\\t")。请访问String parsing in Java with delimeter tab "\t" using split查看讨论。

示例代码：

import java.util.Scanner;

public class ScannerTest
{
    public static void main(String[] args)
    {
        String input = "Some\ttab delimited\tstring\twhere\tsome words\tare\tseparated\tby spaces.";
        Scanner sc = new Scanner(input).useDelimiter("\\t");
        while (sc.hasNext())
        {
            System.out.println(sc.next());
        }
        sc.close();
    }
}

输出：

Some
tab delimited
string
where
some words
are
separated
by spaces.

Answer 2

不要将字符串与等号进行比较，在if子句中使用== ()。在您的例子中，没有打印，因为if子句中的条件返回false，因为您从scanner返回的字符串和您分配给"currenttarget“的字符串将通过引用进行比较，这两个引用是不同的。

错误：

if((list.get(testingtarget) == currenttarget) && (list.get(testingfeature) == currentfeaturetype))

正确：

if((list.get(testingtarget).equals(currenttarget)) && (list.get(testingfeature).equals(currentfeaturetype)))

Answer 3

也许你需要在打印结束后刷新并关闭你的打印器，尝试在writer.flush()；和writer.close()；之前使用multiplier = multiplier +1；并且不要使用==来比较使用等于的字符串