前段时间需要读报表打印,需求是可以从第N行读到第N行,发现百度出来的LineNumberReader方法都不怎么理想然后就找到一篇和众百度里脱颖而出的好文章,所以分享之: 从类 的命名来看,貌似LineNumberReader可以支持从任意行读取的功能,并且提供了setLineNumber()的方法,但是这个按照并不能改变文件指针的位置,只是你调用getLineNumber()这个函数时,结果会变。API上面说它并不能改变文件物理的指针位置。看来以后得小心使用。
import java.io.File;
import java.io.FileInputStream;import java.io.FileNotFoundException;import java.io.FileReader;import java.io.IOException;import java.io.InputStream;import java.io.InputStreamReader;import java.io.LineNumberReader; public class Ex7 { public void dataReader(String nameFile, int start, int finish) { if (start > finish) { System.out.println(“Error start or finish!”); return; } InputStream inputStream = null; LineNumberReader reader = null; try { inputStream = new FileInputStream(new File(nameFile)); reader = new LineNumberReader( new InputStreamReader(inputStream)); int lines = getTotalLines(new File(nameFile)); if (start < 0 || finish < 0 || finish > lines || start > lines) { System.out.println(“Line not found!”); return; } String line = reader.readLine(); lines = 0; while (line != null) { lines++; if(lines >= start && lines <= finish){ System.out.println(line); } line = reader.readLine(); } inputStream.close(); reader.close(); } catch (FileNotFoundException e) { e.printStackTrace(); } catch (IOException e) { System.err.println(“IO Error”); System.exit(0); } } private int getTotalLines(File file) throws IOException{ FileReader in = new FileReader(file); LineNumberReader reader = new LineNumberReader(in); String line = reader.readLine(); int lines = 0; while (line != null) { lines++; line = reader.readLine(); } reader.close(); in.close(); return lines; } public static void main(String[] args) { new Ex7().dataReader(“data.txt”, 2, 4); new Ex7().dataReader(“data.txt”,3,8); }}