Question

我正在尝试将.txt文件中的一行读入一维数组，再添加两个元素到基于该数组的数据，并将新的和更大的数据存储在名为“dataArrayList”的2D ArrayList中，然后重复.txt文件中的后续行。

public static ArrayList<String[]> dataArrayList = new ArrayList<>();

public static void readFile() throws Exception {
    fileRead = new FileReader(txtFileLocation);
    dataReader = new BufferedReader(fileRead);

    String line = "";

    String[] temp;
    String[] temp2 = new String[15];

    //reading the text file
    for (int i = 0; line != null; i++) {
        line = dataReader.readLine();
        if (line != null) {

            //line has 13 Strings to split
            temp = line.split(",");

            //making a larger duplicate with 15 indices instead of 13 as to add 2 more Strings
            System.arraycopy(temp, 0, temp2, 0, temp.length);

            /*
            my code to assign values to the two new 
            elements based data from the previous ones
            */

            //adding temp2 to my ArrayList
            dataArrayList.add(temp2);
        }
    }
}

它似乎应该可以工作，但是当我之后访问dataArrayList时，无论是打印出来还是将其放入JTable，所有记录都是.txt文件最后一行的副本。

例如，如果.txt文件看起来像这样（对于非预期的语法突出显示道歉）：

Hello,my,name,is,Hunter,how,are,you,doing,on,a,lovely,day,like,this
Have,you,heard,about,the,weather,we're,supposed,to,get,a,lot,of,rain,later
Hopefully,it's,sunny,for,the,entire,day,tomorrow,I,have,a,soccer,game,that,day

第一次添加记录时，dataArrayList看起来像你期望的那样，如下所示：

Hello,my,name,is,Hunter,how,are,you,doing,on,a,lovely,day,like,this

然而，在它第二次运行并“添加”第二行后，它看起来像这样：

Have,you,heard,about,the,weather,we're,supposed,to,get,a,lot,of,rain,later
Have,you,heard,about,the,weather,we're,supposed,to,get,a,lot,of,rain,later

最后，在添加第三条记录后，它看起来像这样：

Hopefully,it's,sunny,for,the,entire,day,tomorrow,I,have,a,soccer,game,that,day
Hopefully,it's,sunny,for,the,entire,day,tomorrow,I,have,a,soccer,game,that,day
Hopefully,it's,sunny,for,the,entire,day,tomorrow,I,have,a,soccer,game,that,day

我不明白发生了什么......看起来它正在用当前的记录覆盖以前的记录。

Answer 1

添加temp2 = new String[15];作为循环的最后一行

for (int i = 0; line != null; i++) {
        line = dataReader.readLine();
        if (line != null) {

            //line has 13 Strings to split
            temp = line.split(",");

            //making a larger duplicate with 15 indices instead of 13 as to add 2 more Strings
            System.arraycopy(temp, 0, temp2, 0, temp.length);

            /*
            my code to assign values to the two new 
            elements based data from the previous ones
            */

            //adding temp2 to my ArrayList
            dataArrayList.add(temp2);
            temp2 = new String[15];
        }
    }

Answer 2

以下代码行修改变量temp2的内容

    <?php
    $type=htmlspecialchars($_POST["type"]);
    if ($type=="1")
    {
        echo "1-one\n";//Ends-with \n for client side getting data from server side response
        echo "3-three\n";//Ends-with \n for client side getting data from server side response
        echo "5-five\n";//Ends-with \n for client side getting data from server side response
        echo "7-seven\n";//Ends-with \n for client side getting data from server side response
    }
    else
    {
        if ($type=="0")
        {   echo "2-two\n";//Ends-with \n for client side getting data from server side response
            echo "4-four\n";//Ends-with \n for client side getting data from server side response
            echo "6-six\n";//Ends-with \n for client side getting data from server side response
            echo "8-eight\n";//Ends-with \n for client side getting data from server side response
        }
    }       
?>

您将相同的变量连续添加到列表

   System.arraycopy(temp, 0, temp2, 0, temp.length);

这就是为什么temp2包含文本文件的最后一行，而list只是重复同一行。
我建议

   dataArrayList.add(temp2);

无法在2D ArrayList

2 个答案: