每次调用函数时，从文件读取一行 [英] Read one line at time from a file when a function is called each time
问题描述
String time = Read_one_Line（）;
public static String Read_one_Line（）抛出FileNotFoundException，IOException异常
{
FileInputStream fin = new FileInputStream（sample.txt）;
BufferedReader br = new BufferedReader（new InputStreamReader（fin））;
str = br.readLine（）;
next_line = br.readLine（）;
return next_line;
每次从文本文件中读取一行称为sample.txt和返回。下一次它应该返回下一行，等等....
sample.txt的内容是：
Date：0 Year：0 Hour：0 Minute：0 Seconds：0 MilliSeconds：310
$ b Date：0 Year：0 Hour ：0分钟：0秒：0毫秒：0
日期：0年：0小时：0分钟：0秒：0毫秒：10
日期：0年： 0小时：0分钟：0秒：0毫秒：0
日期：0年：0小时：0分钟：0秒：0毫秒：380
日期：0年份：0小时：0分钟：0秒：10毫秒：-840
日期：0年份：0小时：0分钟：0秒：0毫秒：0
日期：0年份：0小时：0分钟：0秒：0毫秒：0
日期：0年份：0小时：0分钟：0秒：0毫秒：0
Date：0 Year：0 Hour：0 Minute：0 Seconds：0 MilliSeconds：0
但是而是每次只阅读和返回第一行..请告诉米e如何增加到下一行，并在下一次调用这个函数的时候返回它。
你正在创建一个新的 FileInputStream 每次调用函数。因此，每次从头开始读取文件。
仅在函数之外创建 BufferedReader 并在每次调用时传递它，以便连续读取文件。
public static String Read_one_Line（final BufferedReader br）throws IOException
{
next_line = br.readLine（）;
return next_line;
}
使用情况将会像
static void main（String args []）throws IOException {
FileInputStream fin = new FileInputStream（sample.txt）;
try {
BufferedReader br = new BufferedReader（new InputStreamReader（fin））;
String line = Read_one_Line（br）;
while（line！= null）{
System.out.println（line）;
line = Read_one_Line（br）;
}
} finally {
fin.close（）; //确保我们完成后关闭文件。
$ b注意在这种情况下 Read_one_Line 可以被忽略，并由一个简单的 br.readLine（）替换。
<如果你只想每隔一行，你可以在每个迭代中读两行，比如
String line = Read_one_Line BR）;
while（line！= null）{
System.out.println（line）;
String dummy = Read_one_Line（br）;
line = Read_one_Line（br）;
}
String time=Read_one_Line();
public static String Read_one_Line() throws FileNotFoundException, IOException
{
FileInputStream fin=new FileInputStream("sample.txt");
BufferedReader br=new BufferedReader(new InputStreamReader(fin));
str=br.readLine();
next_line=br.readLine();
return next_line;
}
Each time it should read one line from text file called "sample.txt" and return it. next time it should return next line and so on....
Contents of sample.txt are:
Date:0 Year:0 Hour:0 Minute:0 Seconds:0 MilliSeconds:310
Date:0 Year:0 Hour:0 Minute:0 Seconds:0 MilliSeconds:0
Date:0 Year:0 Hour:0 Minute:0 Seconds:0 MilliSeconds:10
Date:0 Year:0 Hour:0 Minute:0 Seconds:0 MilliSeconds:0
Date:0 Year:0 Hour:0 Minute:0 Seconds:0 MilliSeconds:380
Date:0 Year:0 Hour:0 Minute:0 Seconds:10 MilliSeconds:-840
Date:0 Year:0 Hour:0 Minute:0 Seconds:0 MilliSeconds:0
Date:0 Year:0 Hour:0 Minute:0 Seconds:0 MilliSeconds:0
Date:0 Year:0 Hour:0 Minute:0 Seconds:0 MilliSeconds:0
Date:0 Year:0 Hour:0 Minute:0 Seconds:0 MilliSeconds:0
But rather its reading and returning first line only each time.. please tell me how to increment to next line and return it when i call this function next time.
解决方案 You are creating a new FileInputStream each time the function is called. Therefore, the file is read from the beginning each time.
Create the BufferedReader only once, outside of the function and pass it in on each call, so that the file is successively read.
public static String Read_one_Line(final BufferedReader br) throws IOException
{
next_line=br.readLine();
return next_line;
}
usage would be like
static void main(String args[]) throws IOException {
FileInputStream fin=new FileInputStream("sample.txt");
try {
BufferedReader br=new BufferedReader(new InputStreamReader(fin));
String line = Read_one_Line(br);
while ( line != null ) {
System.out.println(line);
line = Read_one_Line(br);
}
} finally {
fin.close(); // Make sure we close the file when we're done.
}
}
Note that in this case, Read_one_Line could just be omitted and replaced by a simple br.readLine().
If you only want every other line, you can just read two lines in each iteration, like
String line = Read_one_Line(br);
while ( line != null ) {
System.out.println(line);
String dummy = Read_one_Line(br);
line = Read_one_Line(br);
}
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