[英]Read data from a text file using Java
I need to read a text file line by line using Java. 我需要使用Java逐行读取文本文件。 I use available()
method of FileInputStream
to check and loop over the file. 我使用FileInputStream
available()
方法来检查和循环文件。 But while reading, the loop terminates after the line before the last one. 但是在读取时,循环在最后一行之前的行之后终止。 ie , if the file has 10 lines, the loop reads only the first 9 lines. 即 ,如果文件有10行,则循环只读取前9行。 Snippet used : 使用的片段:
while(fis.available() > 0)
{
char c = (char)fis.read();
.....
.....
}
You should not use available()
. 你不应该使用available()
。 It gives no guarantees what so ever. 它无法保证什么。 From the API docs of available()
: 来自available()
的API文档 :
Returns an estimate of the number of bytes that can be read (or skipped over) from this input stream without blocking by the next invocation of a method for this input stream. 返回可以从此输入流中读取(或跳过)的字节数的估计值 ,而不会被下一次调用此输入流的方法阻塞。
You would probably want to use something like 你可能想要使用类似的东西
try {
BufferedReader in = new BufferedReader(new FileReader("infilename"));
String str;
while ((str = in.readLine()) != null)
process(str);
in.close();
} catch (IOException e) {
}
(taken from http://www.exampledepot.com/egs/java.io/ReadLinesFromFile.html ) (摘自http://www.exampledepot.com/egs/java.io/ReadLinesFromFile.html )
How about using Scanner? 使用Scanner怎么样? I think using Scanner is easier 我认为使用Scanner更容易
private static void readFile(String fileName) {
try {
File file = new File(fileName);
Scanner scanner = new Scanner(file);
while (scanner.hasNextLine()) {
System.out.println(scanner.nextLine());
}
scanner.close();
} catch (FileNotFoundException e) {
e.printStackTrace();
}
}
If you want to read line-by-line, use a BufferedReader
. 如果要逐行读取,请使用BufferedReader
。 It has a readLine()
method which returns the line as a String, or null if the end of the file has been reached. 它有一个readLine()
方法,它将该行作为String返回,如果已到达文件的末尾,则返回null。 So you can do something like: 所以你可以这样做:
BufferedReader reader = new BufferedReader(new InputStreamReader(fis));
String line;
while ((line = reader.readLine()) != null) {
// Do something with line
}
(Note that this code doesn't handle exceptions or close the stream, etc) (请注意,此代码不处理异常或关闭流等)
String file = "/path/to/your/file.txt";
try {
BufferedReader br = new BufferedReader(new InputStreamReader(new FileInputStream(file)));
String line;
// Uncomment the line below if you want to skip the fist line (e.g if headers)
// line = br.readLine();
while ((line = br.readLine()) != null) {
// do something with line
}
br.close();
} catch (IOException e) {
System.out.println("ERROR: unable to read file " + file);
e.printStackTrace();
}
You can try FileUtils from org.apache.commons.io.FileUtils, try downloading jar from here 您可以从org.apache.commons.io.FileUtils尝试FileUtils, 尝试从这里下载jar
and you can use the following method: FileUtils.readFileToString("yourFileName"); 并且您可以使用以下方法:FileUtils.readFileToString(“yourFileName”);
Hope it helps you.. 希望它可以帮助你..
你的代码跳过最后一行的原因是因为你把fis.available() > 0
而不是fis.available() >= 0
In Java 8 you could easily turn your text file into a List of Strings with streams by using Files.lines
and collect
: 在Java 8中,您可以使用Files.lines
轻松地将文本文件转换为带有流的字符串列表并collect
:
private List<String> loadFile() {
URI uri = null;
try {
uri = ClassLoader.getSystemResource("example.txt").toURI();
} catch (URISyntaxException e) {
LOGGER.error("Failed to load file.", e);
}
List<String> list = null;
try (Stream<String> lines = Files.lines(Paths.get(uri))) {
list = lines.collect(Collectors.toList());
} catch (IOException e) {
LOGGER.error("Failed to load file.", e);
}
return list;
}
//The way that I read integer numbers from a file is...
import java.util.*;
import java.io.*;
public class Practice
{
public static void main(String [] args) throws IOException
{
Scanner input = new Scanner(new File("cards.txt"));
int times = input.nextInt();
for(int i = 0; i < times; i++)
{
int numbersFromFile = input.nextInt();
System.out.println(numbersFromFile);
}
}
}
user scanner it should work 用户扫描仪它应该工作
Scanner scanner = new Scanner(file);
while (scanner.hasNextLine()) {
System.out.println(scanner.nextLine());
}
scanner.close();
public class ReadFileUsingFileInputStream {
/**
* @param args
*/
static int ch;
public static void main(String[] args) {
File file = new File("C://text.txt");
StringBuffer stringBuffer = new StringBuffer("");
try {
FileInputStream fileInputStream = new FileInputStream(file);
try {
while((ch = fileInputStream.read())!= -1){
stringBuffer.append((char)ch);
}
}
catch (IOException e) {
// TODO Auto-generated catch block
e.printStackTrace();
}
}
catch (FileNotFoundException e) {
// TODO Auto-generated catch block
e.printStackTrace();
}
System.out.println("File contents :");
System.out.println(stringBuffer);
}
}
Try this just a little search in Google 试试这只是在谷歌搜索一下
import java.io.*;
class FileRead
{
public static void main(String args[])
{
try{
// Open the file that is the first
// command line parameter
FileInputStream fstream = new FileInputStream("textfile.txt");
// Get the object of DataInputStream
DataInputStream in = new DataInputStream(fstream);
BufferedReader br = new BufferedReader(new InputStreamReader(in));
String strLine;
//Read File Line By Line
while ((strLine = br.readLine()) != null) {
// Print the content on the console
System.out.println (strLine);
}
//Close the input stream
in.close();
}catch (Exception e){//Catch exception if any
System.err.println("Error: " + e.getMessage());
}
}
}
Try using java.io.BufferedReader like this. 尝试使用像这样的java.io.BufferedReader 。
java.io.BufferedReader br = new java.io.BufferedReader(new java.io.InputStreamReader(new java.io.FileInputStream(fileName)));
String line = null;
while ((line = br.readLine()) != null){
//Process the line
}
br.close();
Yes, buffering should be used for better performance. 是的,应该使用缓冲来获得更好的性能。 Use BufferedReader OR byte[] to store your temp data. 使用BufferedReader OR byte []存储临时数据。
thanks. 谢谢。
public class FilesStrings {
public static void main(String[] args) throws FileNotFoundException, IOException {
FileInputStream fis = new FileInputStream("input.txt");
InputStreamReader input = new InputStreamReader(fis);
BufferedReader br = new BufferedReader(input);
String data;
String result = new String();
while ((data = br.readLine()) != null) {
result = result.concat(data + " ");
}
System.out.println(result);
File file = new File("Path");
FileReader reader = new FileReader(file);
while((ch=reader.read())!=-1)
{
System.out.print((char)ch);
}
This worked for me 这对我有用
Simple code for reading file in JAVA: 在JAVA中读取文件的简单代码:
import java.io.*;
class ReadData
{
public static void main(String args[])
{
FileReader fr = new FileReader(new File("<put your file path here>"));
while(true)
{
int n=fr.read();
if(n>-1)
{
char ch=(char)fr.read();
System.out.print(ch);
}
}
}
}
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