分块读取文件

package filereader;

import java.io.IOException;
import java.io.InputStream;
import java.nio.channels.FileChannel;
import java.util.Arrays;

public class FileReader {
	public static int SIZE = 1024 * 1024 * 5;

	public static String FILENAME = "homeuser.unl";

	public static long bt;

	/**
	 * @param args
	 */
	public static void main(String[] args) {
		try {
			
			 bt = System.currentTimeMillis(); 
			 InputStream is = FileReader.class.getResourceAsStream(FILENAME); 
			 readFile(is);
			 System.out.println(System.currentTimeMillis()-bt+":MS");
			 
		} catch (Exception e) {
			e.printStackTrace();
		}
	}

	public static void readFile(InputStream is) throws IOException {
		byte[] buffer = new byte[SIZE];
		StringBuffer sb = new StringBuffer();
		int r = 0;
		int i = 0;
		while (is.available() > 0) {
			i++;
			String partContent = readPartFile(is, buffer, SIZE,  sb);
			sb = null;
			//System.out.println(i + "\n" + partContent);
		}
		System.out.println("I: " + i);
	}

	public static String readPartFile(InputStream inputStream, byte[] buffer,
			int size, StringBuffer sb) {
		try {
			InputStream is = inputStream;
			int r = is.read(buffer);
			if (r == size) {
				byte[] other;
				int count = 0;
				byte n = (byte) is.read();
				other = new byte[] { n };
				sb.append(new String(buffer));
				sb.append(new String(other));
				while (n != 10 && n != -1) {
					count++;
					n = (byte) is.read();
					other = new byte[] { n };
					sb.append(new String(other));
				}
				if (count != 0) {
					SIZE += count;
				}
				System.out.println("COUNT: " + count);
			} else {
				if (null == sb)
					sb = new StringBuffer();
				zjRead(r, sb, buffer);
			}
			return sb.toString();
		} catch (Exception e) {
			e.printStackTrace();
			return null;
		}
	}

	private static void zjRead(int r, StringBuffer sb, byte[] buffer) {
		byte[] temp = new byte[r];
		System.arraycopy(buffer, 0, temp, 0, r);
		sb.append(new String(temp));
	}

}