java 如何在java中读取字符串（文件）到数组

How to read a String (file) to array in java

提问by Sundhas

Suppose there is a file named as SUN.txt

假设有一个名为 SUN.txt 的文件

File contains : a,b,dd,ss,

文件包含：a、b、dd、ss、

I want to make dynamic array depending upon the number of attributes in file. If ther is a char after comma then array will be of 0-4 i.e of length 5. In the above mentioned case there is no Char which returns 0-3 Array of length 4. I want to read the NULL after comma too.

我想根据文件中的属性数量创建动态数组。如果逗号后有一个字符，则数组将为 0-4，即长度为 5。在上述情况下，没有返回长度为 4 的 0-3 数组的 Char。我也想在逗号后读取 NULL。

How do i do that?

我怎么做？

Sundhas

圣达

回答by Markus Lausberg

You should think about

你应该考虑

• Reading the file into a String
• Splitting the file by separator ','
• Using a list for adding the characters and convert the list to an array, when the list is filled

• 将文件读入字符串
• 通过分隔符“,”分割文件
• 使用列表添加字符并将列表转换为数组，当列表被填充时

回答by Brendon Randall

As Markus said, you want to do something like this..

正如马库斯所说，你想做这样的事情..

//Create a buffred reader so that you can read in the file
    BufferedReader reader = new BufferedReader(new FileReader(new File(
            "\SUN.txt")));
    //The StringBuffer will be used to create a string if your file has multiple lines
    StringBuffer sb = new StringBuffer();
    String line;

    while((line = reader.readLine())!= null)
    {
        sb.append(line);
    }

    //We now split the line on the "," to get a string array of the values
    String [] store = sb.toString().split(",");

I do not quite understand why you would want the NULL after the comma? I am assuming that you mean after the last comma you would like that to be null in your array? I do not quite see the point in that but that is not what the question is.

我不太明白为什么你想要逗号后的 NULL？我假设您的意思是在最后一个逗号之后，您希望数组中的值为空？我不太明白这一点，但这不是问题所在。

If that is the case you wont read in a NULL, if after the comma there was a space, you could read that in.

如果是这种情况，您不会读入 NULL，如果逗号后有一个空格，您可以读入。

If you would like a NULL you would have to add it in yourself at the end so you could do something like

如果你想要一个 NULL 你必须在最后自己添加它，这样你就可以做类似的事情

//Create a buffred reader so that you can read in the file
    BufferedReader reader = new BufferedReader(new FileReader(new File(
            "\SUN.txt")));
    //Use an arraylist to store the values including nulls
    ArrayList<String> store = new ArrayList<String>();
    String line;
    while((line = reader.readLine())!= null)
    {
        String [] splitLine = line.split(",");
        for(String x : splitLine)
        {
            store.add(line);
        }
        //This tests to see if the last character of the line is , and will add a null into the array list
        if(line.endsWith(","))
            store.add(null);
    }

    String [] storeWithNull = store.toArray();

回答by Jason Rogers

Well if you want want to simply open the file and store the content in a array of string then

好吧，如果您只想打开文件并将内容存储在字符串数组中，那么

1) open the file into a string

1) 将文件打开成字符串

2) split the string using a regex "," http://download.oracle.com/javase/1.5.0/docs/api/java/lang/String.html#split(java.lang.String)

2）使用正则表达式“,”分割字符串http://download.oracle.com/javase/1.5.0/docs/api/java/lang/String.html#split(java.lang.String)

but I'm curious why you can't use a String file directly ?

但我很好奇为什么不能直接使用 String 文件？

回答by Andreas Dolk

For your datatructure, use a list of arrays. Each list entry is a line of your textfile, each entry is an array that holds the comma separated values:

对于您的数据结构，请使用数组列表。每个列表条目是文本文件的一行，每个条目是一个包含逗号分隔值的数组：

List<String[]> data = new ArrayList<String[]>();
String line = readNextLine();  // custom method, to be implemented
while (line != null) {
  data.add(line.split(","));
  line = readNextLine();
}

(assuming, your file contains 1..n lines of comma separated values)

（假设您的文件包含 1..n 行逗号分隔值）

---

---

You may want to have it like this:

你可能想要这样：

"a,b,c,d,"  -> {"a", "b", "c", "d", null}

Here's a suggestion how to solve that problem:

以下是如何解决该问题的建议：

List<String[]> data = new ArrayList<String[]>();
String line = readNextLine();  // custom method, to be implemented
while (line != null) {
  String[] values = new String[5];
  String[] pieces = line.split(",");
  for (int i = 0; i<pieces.length; i++)
     values[i] = pieces[i];
  data.add(values);

  line = readNextLine();
}

回答by chinni776

its seems like a CSV file something like this will work assuming it has 5 lines and 5 values

它看起来像一个 CSV 文件，假设它有 5 行和 5 个值，这样的文件会起作用

String [][] value = new String [5][5];
File file = new File("SUN.txt");
BufferedReader br  = new BufferedReader(new FileReader(file));
String line = null;
int row = 0;
int col = 0;

while((line = br.readLine()) != null ){ 
StringTokenizer s = new StringTokenizer(line,",");

    while (s.hasMoreTokens()){
    value[row][col] = s.nextToken();
    col++;
}
col = 0;
row++;
}

i havent tested this code

我还没有测试过这段代码

回答by Camilo Díaz Repka

Read the file, using BufferedReader, one line at the time.

读取文件，使用BufferedReader，一次一行。

Use split(",", -1)to convert to an array of String[]including also empty strings beyond the last comma as part of your array.

使用split(",", -1)转换为数组String[]还包括超越了最后一个逗号空字符串作为阵列的一部分。

Load the String[]parts into a List.

将String[]零件装入List.