java - br.readLine() = ","时生成 ArrayIndexOutOfBoundsException

Question

下面的代码有几个函数，这些函数允许诸如将数据写入文档、读取文档以及将数据放入数组中以用于稍后的 JTable 等操作。

package tabletest.populatetable;

import java.io.BufferedReader;
import java.io.BufferedWriter;
import java.io.File;
import java.io.FileReader;
import java.io.FileWriter;

public class GetData {
    DataClass[] data = new DataClass[500];
    int nextPosition = 0;

    public GetData() {
        readData();
    }

    public void writeData()
    {
        try {
            BufferedWriter bw = new BufferedWriter(new FileWriter(new File("resources/tabledata.txt")));

            for(int i=0; i < nextPosition; i++) {
                bw.write(data[i].toString());
                bw.newLine();
            }

            bw.close();
        } catch(Exception e) {
            System.out.println("Invalid Data input");
        }
    }

    public void readData()
    {
        try {
            BufferedReader br = new BufferedReader(new FileReader(new File("resources/tabledata.txt")));
            String nextData = br.readLine();
            String[] arrayStringData;

            while (nextData != null) {

                try {
                    arrayStringData = nextData.split(",");
                } catch(NullPointerException nPE) {
                    arrayStringData = new String[] {" ", " "};
                }

                for(int i = 0; i < arrayStringData.length - 1; i++) {
                    if(arrayStringData[i] == null || arrayStringData[i] == "") {
                        arrayStringData[i] = " ";
                    }
                }

                DataClass getData = new DataClass();
                getData.col1 = arrayStringData[0].trim();
                getData.col2 = arrayStringData[1].trim();
                data[nextPosition] = getData;
                nextPosition++;
                nextData = br.readLine();
            }

            br.close();
        } catch(Exception e) {
            e.printStackTrace();
        }
    }

    public String[][] dataInTableForm() {
        final int colCount = 2;
        String[][] temp = new String[nextPosition][colCount];

        for(int i = 0; i < nextPosition; i++) {
            temp[i][0] = data[i].col1;
            temp[i][1] = data[i].col2;
        }

        return temp;
    }

    private class DataClass {
        String col1;
        String col2;

        public String toString() {
            return col1 + ", " + col2;
        }
    }
}

它正在读取的文档 resources/tabledata.txt 有 12 行，看起来像这样。

asfias, adsnj
aw,aerfae
aw,aewaa
,tre
asfd, 
okfas,af
e,ds
sw,f
,
asfias, adsnj
aw,aerfae
aw,aewaa

问题出在文本文档的第 9 行。这是它本身只是一个 , 的地方。当逗号之前或之后有东西时，这似乎工作正常，我通过删除该行来检查它是否确实是导致问题的逗号。

当我查看控制台时，我发现问题是 ArrayIndexOutOfBoundsException 并且堆栈跟踪如下。

java.lang.ArrayIndexOutOfBoundsException: 0
    at tabletest.populatetable.GetData.readData(GetData.java:55)
    at tabletest.populatetable.GetData.<init>(GetData.java:14)
    at tabletest.Table.createTablePanel(Table.java:76)
    at tabletest.Table.createPanels(Table.java:34)
    at tabletest.Table.runGUI(Table.java:24)
    at tabletest.Table.main(Table.java:150)

代码的第 55 行是 getData.col1 = arrayStringData[0].trim();

正如您在代码中看到的那样，我尝试了几种方法来防止这种情况发生，但我没有成功。我还尝试从行尾删除 .trim() ；但是，出现了完全相同的问题。

如能帮助解决此问题，我将不胜感激。

Answer 1

split(String regex) 的 Javadoc说:

This method works as if by invoking the two-argument split method with the given expression and a limit argument of zero. Trailing empty strings are therefore not included in the resulting array.

因此，",".split(",") 将返回一个空数组，即 new String[0]。

如果要保留尾随空字符串，请使用 ",".split(",", -1)，它将返回 new String[] { "", ""。