当br.readLine()=","时生成ArrayIndexOutOfBoundsException

Question

下面的代码有几个功能,允许诸如将数据写入文档,读取数据以及将数据放入数组中以便JTable以后使用.

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;
        }
    }
}

它正在阅读的文件resources/tabledata.txt长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

问题出在文本文件的第9行.这是它本身就是一个地方,.当逗号之前或之后有什么东西这似乎工作正常,我通过删除行检查它是否肯定是导致问题的逗号.

当我查看控制台时,我发现问题是a ArrayIndexOutOfBoundsException,堆栈跟踪在下面.

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();

正如你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,但我没有运气.我也尝试.trim()从线的末尾删除; 但是,出现完全相同的问题.

我很感激任何帮助解决这个问题.

Answer 1

Javadoc split(String regex)说:

此方法就像通过split使用给定表达式和limit参数为零调用双参数方法一样工作.因此,结尾的空字符串不包含在结果数组中.

所以,",".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),这将返回new String[] { "", "" }.