[英]Java - Trouble creating a 2D array from a text file
I have a text file that is formatted as a square array. 我有一个格式为方形数组的文本文件。 I am trying to convert this to a 2 dimensional array in Java.
我试图将其转换为Java中的二维数组。 "st" is the text file described below.
“ st”是下面描述的文本文件。
This is my code: 这是我的代码:
public createArray(String st) throws NumberFormatException, IOException {
InputStream is;
is = new FileInputStream(st);
BufferedReader br = new BufferedReader(new InputStreamReader(is, Charset.forName("UTF-8")));
int row = 0;
while ((line = br.readLine()) != null){
String[] nums = line.split(" ");
for (int col = 0; col < nums.length; col++){
int n = Integer.parseInt(nums[col]);
myArray[row][col] = n;
}
row++;
}
I am getting a null pointer exception on the line: 我在行上得到一个空指针异常:
myArray[row][col] = n;
If I print out the values of row, col, and n at each iteration, they appear to coincide correctly. 如果我在每次迭代中打印出row,col和n的值,它们似乎正确重合。 However, I am still getting a NullPointerException.
但是,我仍然收到NullPointerException。
The text file is formatted as: 文本文件的格式为:
1 2 3 4 5 6 7 8 9 10
11 12 13 14 15 16 17 18 19 20
21 22 23 24 25 26 27 28 29 30
31 32 33 34 35 36 37 38 39 40
41 42 43 44 45 46 47 48 49 50
51 52 53 54 55 56 57 58 59 60
61 62 63 64 65 66 67 68 69 70
71 72 73 74 75 76 77 78 79 80
81 82 83 84 85 86 87 88 89 90
91 92 93 94 95 96 97 98 99 0
I think you have not initialized int[][] myArray;
我认为您尚未初始化
int[][] myArray;
You should do something like this 你应该做这样的事情
int[][] myArray = new int[100][100];
OR 要么
find the total rows in the file and initialize the row. 在文件中查找总行并初始化该行。 And in each loop calculate the column and create the desired array
并在每个循环中计算列并创建所需的数组
int[][] myArray;
{
int rows = getTotalRows();
myArray = new int[rows][];
}
then 然后
while ((line = br.readLine()) != null){
String[] nums = line.split(" ");
myArray[row] = new int[nums.length]; //initialize dynamically here
for (int col = 0; col < nums.length; col++){
int n = Integer.parseInt(nums[col]);
myArray[row][col] = n;
}
row++;
}
Regards to your comment you didn't initiate array. 关于您的评论,您没有启动数组。
int[][] myArray = new int[100][]; // enough to define rows
Other way: 另一种方式:
If you use Java 7 you can load text file to List
. 如果使用Java 7,则可以将文本文件加载到
List
。 As I know this is a shortest way to create String[][]
据我所知,这是创建
String[][]
的最短方法
String[][] myArray;
List<String> lines = Files.readAllLines(Paths.get("<your filename>"), StandardCharsets.UTF_8);
myArray = new String[lines.size()][];
for(int i =0; i<lines.size(); i++){
myArray[i] = lines.get(i).split("[ ]+"); // you can use just split(" ") but who knows how many empty spaces
}
Now you have populated myArray[][]
现在,您已填充
myArray[][]
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