Java读取大文件

 1 public static void main2(String[] args) throws Exception {
 2   int bufSize = 1024;
 3   byte[] bs = new byte[bufSize];
 4   ByteBuffer byteBuf = ByteBuffer.allocate(1024);
 5   FileChannel channel = new RandomAccessFile(fff, "r").getChannel();
 6   while (channel.read(byteBuf) != -1) {
 7    int size = byteBuf.position();
 8    byteBuf.rewind();
 9    byteBuf.get(bs); // 把文件当字符串处理，直接打印做为一个例子。
10    System.out.print(new String(bs, 0, size));
11    byteBuf.clear();
12   }
13 
14 }

1 public static void main(String[] args) throws Exception {
2   BufferedReader br = new BufferedReader(new FileReader(fff));
3   String line = null;
4   while ((line = br.readLine()) != null) {
5    System.out.println(line);
6   }
7 }

 1 public static void main(String[] args) throws Exception {
 2     int bufSize = 1024;
 3     byte[] bs = new byte[bufSize];
 4     ByteBuffer byteBuf = ByteBuffer.allocate(1024);
 5     FileChannel channel = new RandomAccessFile("d:\\filename","r").getChannel();
 6     while(channel.read(byteBuf) != -1) {
 7       int size = byteBuf.position();
 8       byteBuf.rewind();
 9       byteBuf.get(bs);
10       // 把文件当字符串处理，直接打印做为一个例子。
11       System.out.print(new String(bs, 0, size));
12       byteBuf.clear();
13     }
14   }
15 
16 }

 1 import java.io.BufferedReader;
 2 import java.io.FileNotFoundException;
 3 import java.io.FileReader;
 4 import java.io.IOException;
 5 import java.io.RandomAccessFile;
 6 import java.util.Scanner;
 7 
 8 public class TestPrint {
 9     public static void main(String[] args) throws IOException {
10         String path = "你要读的文件的路径";
11         RandomAccessFile br=new RandomAccessFile(path,"rw");//这里rw看你了。要是之都就只写r
12         String str = null, app = null;
13         int i=0;
14         while ((str = br.readLine()) != null) {
15             i++;
16             app=app+str;
17             if(i>=100){//假设读取100行
18                 i=0;
19 //                这里你先对这100行操作，然后继续读
20 app=null;
21             }
22         }
23         br.close();
24     }
25 
26 }

 1 void largeFileIO(String inputFile, String outputFile) {
 2         try {
 3             BufferedInputStream bis = new BufferedInputStream(new FileInputStream(new File(inputFile)));
 4             BufferedReader in = new BufferedReader(new InputStreamReader(bis, "utf-8"), 10 * 1024 * 1024);//10M缓存
 5             FileWriter fw = new FileWriter(outputFile);
 6             while (in.ready()) {
 7                 String line = in.readLine();
 8                 fw.append(line + " ");
 9             }
10             in.close();
11             fw.flush();
12             fw.close();
13         } catch (IOException ex) {
14             ex.printStackTrace();
15         }

1 File file = new File(filepath);   
2 BufferedInputStream fis = new BufferedInputStream(new FileInputStream(file));    
3 BufferedReader reader = new BufferedReader(new InputStreamReader(fis,"utf-8"),5*1024*1024);// 用5M的缓冲读取文本文件  
4   
5 String line = "";
6 while((line = reader.readLine()) != null){
7 //TODO: write your business
8 }