我需要根据条件将一行从文件复制到另一个
这是我的代码
import org.apache.commons.io.FileUtils;
public class FileCopy {
public static void main(String args[]) throws IOException {
File source = \\
File fileToCopyFrom \\
File target :\\
if (!target.exists()) {
target.createNewFile();
}
PrintStream fstream =new PrintStream(target);
BufferedReader brSource = new BufferedReader(new FileReader(source));
BufferedReader brFileToCopyFrom = new BufferedReader(new FileReader(fileToCopyFrom));
String lineSource;
String lineToCopy;
while((lineSource = brSource.readLine()) != null) {
while ((lineToCopy=brFileToCopyFrom.readLine())!=null) {
if (lineToCopy.contains(lineSource.substring(lineSource.indexOf("_")+1, lineSource.indexOf(".")-1)))
fstream.println(lineToCopy);
}
}
}}
但它只复制第一行
错误在哪里?
最佳答案
仅复制第一个,因为在第一个while
的第二次迭代中,brFileToCopyFrom
到达了文件末尾。
您需要在第一个BufferedReader brFileToCopy
(示例1)内打开while
或使用mark/reset
功能(示例2)。
范例1:
while ((lineSource = brSource.readLine()) != null) {
BufferedReader brFileToCopyFrom = new BufferedReader(new FileReader(fileToCopyFrom));
while ((lineToCopy = brFileToCopyFrom.readLine()) != null) {
...
}
}
}
范例2:
brFileToCopyFrom.mark(1024); // number of characters to be read while preserving the mark
while ((lineSource = brSource.readLine()) != null) {
brFileToCopyFrom.reset();
while ((lineToCopy = brFileToCopyFrom.readLine()) != null) {
...
}
}
}