JAVA IO - 得到文件行數

import java.io.File;
import java.io.FileReader;
import java.io.LineNumberReader;


public class FileLinelength {
    public static void main(String args[]) throws Exception{
    	File file = new File("C:\\work\\hello\\helloworld.txt");
    	FileReader reader = new FileReader(file);
    	LineNumberReader  lineReader = new LineNumberReader(reader);
    	int length = 0;
    	while(lineReader.readLine()!= null){
    		length++;
    	}
    	System.out.println("This file line number is " + length);
    }
}

Perforcemance比較高的方法

public int count(String filename) throws IOException {
    InputStream is = new BufferedInputStream(new FileInputStream(filename));
    try {
        byte[] c = new byte[1024];
        int count = 0;
        int readChars = 0;
        boolean empty = true;
        while ((readChars = is.read(c)) != -1) {
            empty = false;
            for (int i = 0; i < readChars; ++i) {
                if (c[i] == '\n') {
                    ++count;
                }
            }
        }
        return (count == 0 && !empty) ? 1 : count;
    } finally {
        is.close();
    }
}

LineNumberReader  lnr = new LineNumberReader(new FileReader(new File("File1")));
lnr.skip(Long.MAX_VALUE);
System.out.println(lnr.getLineNumber());