BufferedReader br = new BufferedReader(new InputStreamReader(new FileInputStream("ming.txt")));
String data = null;
while((data = br.readLine())!=null)
{
System.out.println(data); 
}

package com.sty.tools.fileutil;

import java.io.File;
import java.io.FileInputStream;
import java.io.FileNotFoundException;
import java.io.FileOutputStream;
import java.io.IOException;
import java.io.InputStreamReader;

public class FileOperatorTest {
    /**
     * @param args
     */
    public static void main(String[] args) {
        // TODO Auto-generated method stub
        // file(内存)----输入流---->【程序】----输出流---->file(内存)
        
        String path="d:\\temp\\";
        String fileName="addfile.txt";
        //File file = new File("d:\\temp\\addfile.txt");
        
        File file = createFile2(path,fileName);

        // 向文件写入内容(输出流)
        String str = "亲爱的小南瓜！";
        byte bt[] = new byte[1024];
        bt = str.getBytes();
        try {
            FileOutputStream in = new FileOutputStream(file);
            try {
                in.write(bt, 0, bt.length);
                in.close();
                // boolean success=true;
                // System.out.println("写入文件成功");
            } catch (IOException e) {
                // TODO Auto-generated catch block
                e.printStackTrace();
            }
        } catch (FileNotFoundException e) {
            // TODO Auto-generated catch block
            e.printStackTrace();
        }
        try {
            // 读取文件内容 (输入流)
            FileInputStream out = new FileInputStream(file);
            InputStreamReader isr = new InputStreamReader(out);
            int ch = 0;
            while ((ch = isr.read()) != -1) {
                System.out.print((char) ch);
            }
        } catch (Exception e) {
            // TODO: handle exception
        }
    }
    
    public static File createFile(String path,String fileName){
        File folder = new File(path);
        if(!folder.exists()){
            folder.mkdir();
        }
        File file = new File(path+fileName);
        if(!file.exists()){
            try {
                file.createNewFile();
            } catch (IOException e) {
                // TODO Auto-generated catch block
                e.printStackTrace();
            }
        }
        return file;
    }
    
    public static File createFile2(String path,String fileName){
        File file = new File(path,fileName);
        file.getParentFile().mkdirs();
        if(!file.exists()){
            try {
                file.createNewFile();
            } catch (IOException e) {
                // TODO Auto-generated catch block
                e.printStackTrace();
            }
        }
        return file;
    }
}

package com.sty.tools.fileutil;

//------------------参考资料---------------------------------
//
//1、按字节读取文件内容
//2、按字符读取文件内容 （此可以避免乱码问题）
//3、按行读取文件内容  
//4、随机读取文件内容

import java.io.BufferedReader;
import java.io.File;
import java.io.FileInputStream;
import java.io.FileReader;
import java.io.IOException;
import java.io.InputStream;
import java.io.InputStreamReader;
import java.io.RandomAccessFile;
import java.io.Reader;

public class ReadFromFile {
    /**
     * 以字节为单位读取文件，常用于读二进制文件，如图片、声音、影像等文件。
     * 
     * @param fileName
     *            文件的名
     */
    public static void readFileByBytes(String fileName) {
        File file = new File(fileName);
        InputStream in = null;
        try {
            System.out.println("以字节为单位读取文件内容，一次读一个字节：");
            // 一次读一个字节
            in = new FileInputStream(file);
            int tempbyte;
            while ((tempbyte = in.read()) != -1) {
                System.out.write(tempbyte);
            }
            in.close();
        } catch (IOException e) {
            e.printStackTrace();
            return;
        }
        try {
            System.out.println("以字节为单位读取文件内容，一次读多个字节：");
            // 一次读多个字节
            byte[] tempbytes = new byte[100];
            int byteread = 0;
            in = new FileInputStream(fileName);
            ReadFromFile.showAvailableBytes(in);
            // 读入多个字节到字节数组中，byteread为一次读入的字节数
            while ((byteread = in.read(tempbytes)) != -1) {
                System.out.write(tempbytes, 0, byteread);
            }
        } catch (Exception e1) {
            e1.printStackTrace();
        } finally {
            if (in != null) {
                try {
                    in.close();
                } catch (IOException e1) {
                }
            }
        }
    }

    /**
     * 以字符为单位读取文件，常用于读文本，数字等类型的文件
     * 
     * @param fileName
     *            文件名
     */
    public static void readFileByChars(String fileName) {
        File file = new File(fileName);
        Reader reader = null;
        try {
            System.out.println("以字符为单位读取文件内容，一次读一个字节：");
            // 一次读一个字符
            reader = new InputStreamReader(new FileInputStream(file),"gbk");
            int tempchar;
            while ((tempchar = reader.read()) != -1) {
                // 对于windows下，rn这两个字符在一起时，表示一个换行。
                // 但如果这两个字符分开显示时，会换两次行。
                // 因此，屏蔽掉r，或者屏蔽n。否则，将会多出很多空行。
                if (((char) tempchar) != ‘r‘) {
                    System.out.print((char) tempchar);
                }
            }
            reader.close();
        } catch (Exception e) {
            e.printStackTrace();
        }
        try {
            System.out.println("以字符为单位读取文件内容，一次读多个字节：");
            // 一次读多个字符
            char[] tempchars = new char[30];
            int charread = 0;
            reader = new InputStreamReader(new FileInputStream(fileName),"gbk");
            // 读入多个字符到字符数组中，charread为一次读取字符数
            while ((charread = reader.read(tempchars)) != -1) {
                // 同样屏蔽掉r不显示
                if ((charread == tempchars.length)
                        && (tempchars[tempchars.length - 1] != ‘r‘)) {
                    System.out.print(tempchars);
                } else {
                    for (int i = 0; i < charread; i++) {
                        if (tempchars[i] == ‘r‘) {
                            continue;
                        } else {
                            System.out.print(tempchars[i]);
                        }
                    }
                }
            }
        } catch (Exception e1) {
            e1.printStackTrace();
        } finally {
            if (reader != null) {
                try {
                    reader.close();
                } catch (IOException e1) {
                }
            }
        }
    }

    /**
     * 以行为单位读取文件，常用于读面向行的格式化文件
     * 
     * @param fileName
     *            文件名
     */
    public static void readFileByLines(String fileName) {
        File file = new File(fileName);
        BufferedReader reader = null;
        try {
            System.out.println("以行为单位读取文件内容，一次读一整行：");
            reader = new BufferedReader(new FileReader(file));
            String tempString = null;
            int line = 1;
            // 一次读入一行，直到读入null为文件结束
            while ((tempString = reader.readLine()) != null) {
                // 显示行号
                System.out.println("line " + line + ": " + tempString);
                line++;
            }
            reader.close();
        } catch (IOException e) {
            e.printStackTrace();
        } finally {
            if (reader != null) {
                try {
                    reader.close();
                } catch (IOException e1) {
                }
            }
        }
    }

    /**
     * 随机读取文件内容
     * 
     * @param fileName
     *            文件名
     */
    public static void readFileByRandomAccess(String fileName) {
        RandomAccessFile randomFile = null;
        try {
            System.out.println("随机读取一段文件内容：");
            // 打开一个随机访问文件流，按只读方式
            randomFile = new RandomAccessFile(fileName, "r");
            // 文件长度，字节数
            long fileLength = randomFile.length();
            // 读文件的起始位置
            int beginIndex = (fileLength > 4) ? 4 : 0;
            // 将读文件的开始位置移到beginIndex位置。
            randomFile.seek(beginIndex);
            byte[] bytes = new byte[10];
            int byteread = 0;
            // 一次读10个字节，如果文件内容不足10个字节，则读剩下的字节。
            // 将一次读取的字节数赋给byteread
            while ((byteread = randomFile.read(bytes)) != -1) {
                System.out.write(bytes, 0, byteread);
            }
        } catch (IOException e) {
            e.printStackTrace();
        } finally {
            if (randomFile != null) {
                try {
                    randomFile.close();
                } catch (IOException e1) {
                }
            }
        }
    }

    /**
     * 显示输入流中还剩的字节数
     * 
     * @param in
     */
    private static void showAvailableBytes(InputStream in) {
        try {
            System.out.println("当前字节输入流中的字节数为:" + in.available());
        } catch (IOException e) {
            e.printStackTrace();
        }
    }

    public static void main(String[] args) {
        String fileName = "E:\\桌面文件备份2015年6月11日104137\\centOS命令.txt";
        //ReadFromFile.readFileByBytes(fileName);
        ReadFromFile.readFileByChars(fileName);
        //ReadFromFile.readFileByLines(fileName);
        //ReadFromFile.readFileByRandomAccess(fileName);
    }
}

//二、将内容追加到文件尾部  
import java.io.FileWriter;  
import java.io.IOException;  
import java.io.RandomAccessFile;  
  
/** 
 * 将内容追加到文件尾部 
 */  
public class AppendToFile {  
    /** 
     * A方法追加文件：使用RandomAccessFile 
     *  
     * @param fileName 
     *            文件名 
     * @param content 
     *            追加的内容 
     */  
    public static void appendMethodA(String fileName,  
  
    String content) {  
        try {  
            // 打开一个随机访问文件流，按读写方式  
            RandomAccessFile randomFile = new RandomAccessFile(fileName, "rw");  
            // 文件长度，字节数  
            long fileLength = randomFile.length();  
            // 将写文件指针移到文件尾。  
            randomFile.seek(fileLength);  
            randomFile.writeBytes(content);  
            randomFile.close();  
        } catch (IOException e) {  
            e.printStackTrace();  
        }  
    }  
  
    /** 
     * B方法追加文件：使用FileWriter 
     *  
     * @param fileName 
     * @param content 
     */  
    public static void appendMethodB(String fileName, String content) {  
        try {  
            // 打开一个写文件器，构造函数中的第二个参数true表示以追加形式写文件  
            FileWriter writer = new FileWriter(fileName, true);  
            writer.write(content);  
            writer.close();  
        } catch (IOException e) {  
            e.printStackTrace();  
        }  
    }  
  
    public static void main(String[] args) {  
        String fileName = "C:/temp/newTemp.txt";  
        String content = "new append!";  
        // 按方法A追加文件  
        AppendToFile.appendMethodA(fileName, content);  
        AppendToFile.appendMethodA(fileName, "append end. n");  
        // 显示文件内容  
        ReadFromFile.readFileByLines(fileName);  
        // 按方法B追加文件  
        AppendToFile.appendMethodB(fileName, content);  
        AppendToFile.appendMethodB(fileName, "append end. n");  
        // 显示文件内容  
        ReadFromFile.readFileByLines(fileName);  
    }  
}  

package com.sty.tools.fileutil;

import java.io.File;     
import java.io.IOException;

import java.io.FileOutputStream;     
  
import java.io.*;     

public class WriteFileTest { 
    
    public static void main(String[] args) {     
        FileOutputStream out = null;     
        FileOutputStream outSTr = null;     
        BufferedOutputStream Buff=null;     
        FileWriter fw = null;     
        int count=1000;//写文件行数     
        try {     
            out = new FileOutputStream(createFile("d://temp//","add.txt"));     
            long begin = System.currentTimeMillis();     
            for (int i = 0; i < count; i++) {     
                out.write("测试java 文件操作\r\n".getBytes());     
            }      
            out.close();      
            long end = System.currentTimeMillis();     
            System.out.println("FileOutputStream执行耗时:" + (end - begin) + " 豪秒"); 
            
            outSTr = new FileOutputStream(createFile("d://temp//","add1.txt"));     
            Buff=new BufferedOutputStream(outSTr);     
            long begin0 = System.currentTimeMillis();     
            for (int i = 0; i < count; i++) {     
                Buff.write("测试java 文件操作\r\n".getBytes());     
            }     
            Buff.flush();     
            Buff.close();     
            long end0 = System.currentTimeMillis();     
            System.out.println("BufferedOutputStream执行耗时:" + (end0 - begin0) + " 豪秒");
            
            fw = new FileWriter(createFile("d://temp//","add2.txt"));     
            long begin3 = System.currentTimeMillis();     
            for (int i = 0; i < count; i++) {     
                fw.write("测试java 文件操作\r\n");     
            }      
            fw.close();     
            long end3 = System.currentTimeMillis();     
            System.out.println("FileWriter执行耗时:" + (end3 - begin3) + " 豪秒");     
        } catch (Exception e) {     
            e.printStackTrace();     
        }     
        finally {     
            try {     
                fw.close();     
                Buff.close();     
                outSTr.close();     
                out.close();     
            } catch (Exception e) {     
                e.printStackTrace();     
            }     
        }     
    }  
    
    public static File createFile(String path,String fileName){
        File folder = new File(path);
        if(!folder.exists()){
            folder.mkdir();
        }
        File file = new File(path+fileName);
        if(!file.exists()){
            try {
                file.createNewFile();
            } catch (IOException e) {
                // TODO Auto-generated catch block
                e.printStackTrace();
            }
        }
        return file;
    }
}  

public class BufferedInputStream extends FilterInputStream {  
    private static int defaultBufferSize = 2048;   
    protected byte buf[]; // 建立读缓存区  
    public BufferedInputStream(InputStream in, int size) {  
        super(in);          
        if (size <= 0) {  
            throw new IllegalArgumentException("Buffer size <= 0");  
        }  
        buf = new byte[size];  
    }  
    public synchronized int read() throws IOException {  
        ensureOpen();  
        if (pos >= count) {  
            fill();  
            if (pos >= count)  
                return -1;  
        }  
        return buf[pos++] & 0xff; // 直接从BUF[]中读取  
    }   
    private void fill() throws IOException {  
    if (markpos < 0)  
        pos = 0;        /* no mark: throw away the buffer */  
    else if (pos >= buf.length)  /* no room left in buffer */  
        if (markpos > 0) {   /* can throw away early part of the buffer */  
        int sz = pos - markpos;  
        System.arraycopy(buf, markpos, buf, 0, sz);  
        pos = sz;  
        markpos = 0;  
        } else if (buf.length >= marklimit) {  
        markpos = -1;   /* buffer got too big, invalidate mark */  
        pos = 0;    /* drop buffer contents */  
        } else {        /* grow buffer */  
        int nsz = pos * 2;  
        if (nsz > marklimit)  
            nsz = marklimit;  
        byte nbuf[] = new byte[nsz];  
        System.arraycopy(buf, 0, nbuf, 0, pos);  
        buf = nbuf;  
        }  
    count = pos;  
    int n = in.read(buf, pos, buf.length - pos);  
    if (n > 0)  
        count = n + pos;  
    }  
}  

public class BufferedOutputStream extends FilterOutputStream {  
   protected byte buf[]; // 建立写缓存区  
   public BufferedOutputStream(OutputStream out, int size) {  
        super(out);  
        if (size <= 0) {  
            throw new IllegalArgumentException("Buffer size <= 0");  
        }  
        buf = new byte[size];  
    }   
public synchronized void write(int b) throws IOException {  
        if (count >= buf.length) {  
            flushBuffer();  
        }  
        buf[count++] = (byte)b; // 直接从BUF[]中读取  
   }  
   private void flushBuffer() throws IOException {  
        if (count > 0) {  
            out.write(buf, 0, count);  
            count = 0;  
        }  
   }  
}  

public class BufferedRandomAccessFile extends RandomAccessFile {  
//  byte read(long pos)：读取当前文件POS位置所在的字节  
//  bufstartpos、bufendpos代表BUF映射在当前文件的首/尾偏移地址。  
//  curpos指当前类文件指针的偏移地址。  
    public byte read(long pos) throws IOException {  
        if (pos < this.bufstartpos || pos > this.bufendpos ) {  
            this.flushbuf();  
            this.seek(pos);  
            if ((pos < this.bufstartpos) || (pos > this.bufendpos))   
                throw new IOException();  
        }  
        this.curpos = pos;  
        return this.buf[(int)(pos - this.bufstartpos)];  
    }  
// void flushbuf()：bufdirty为真，把buf[]中尚未写入磁盘的数据，写入磁盘。  
    private void flushbuf() throws IOException {  
        if (this.bufdirty == true) {  
            if (super.getFilePointer() != this.bufstartpos) {  
                super.seek(this.bufstartpos);  
            }  
            super.write(this.buf, 0, this.bufusedsize);  
            this.bufdirty = false;  
        }  
    }  
// void seek(long pos)：移动文件指针到pos位置，并把buf[]映射填充至POS所在的文件块。  
    public void seek(long pos) throws IOException {  
        if ((pos < this.bufstartpos) || (pos > this.bufendpos)) { // seek pos not in buf  
            this.flushbuf();  
            if ((pos >= 0) && (pos <= this.fileendpos) && (this.fileendpos != 0)) {   // seek pos in file (file length > 0)  
                  this.bufstartpos =  pos * bufbitlen / bufbitlen;  
                  this.bufusedsize = this.fillbuf();  
            } else if (((pos == 0) && (this.fileendpos == 0)) || (pos == this.fileendpos + 1)) {   // seek pos is append pos  
                this.bufstartpos = pos;  
                this.bufusedsize = 0;  
            }  
            this.bufendpos = this.bufstartpos + this.bufsize - 1;  
        }  
        this.curpos = pos;  
    }  
// int fillbuf()：根据bufstartpos，填充buf[]。  
    private int fillbuf() throws IOException {  
        super.seek(this.bufstartpos);  
        this.bufdirty = false;  
        return super.read(this.buf);  
    }  
}  

// boolean write(byte bw, long pos)：向当前文件POS位置写入字节BW。  
// 根据POS的不同及BUF的位置：存在修改、追加、BUF中、BUF外等情况。在逻辑判断时，把最可能出现的情况，最先判断，这样可提高速度。  
// fileendpos：指示当前文件的尾偏移地址，主要考虑到追加因素  
    public boolean write(byte bw, long pos) throws IOException {  
        if ((pos >= this.bufstartpos) && (pos <= this.bufendpos)) { // write pos in buf  
            this.buf[(int)(pos - this.bufstartpos)] = bw;  
            this.bufdirty = true;  
            if (pos == this.fileendpos + 1) { // write pos is append pos  
                this.fileendpos++;  
                this.bufusedsize++;  
            }  
        } else { // write pos not in buf  
            this.seek(pos);  
            if ((pos >= 0) && (pos <= this.fileendpos) && (this.fileendpos != 0)) { // write pos is modify file  
                this.buf[(int)(pos - this.bufstartpos)] = bw;  
            } else if (((pos == 0) && (this.fileendpos == 0)) || (pos == this.fileendpos + 1)) { // write pos is append pos  
                this.buf[0] = bw;  
                this.fileendpos++;  
                this.bufusedsize = 1;  
            } else {  
                throw new IndexOutOfBoundsException();  
            }  
            this.bufdirty = true;  
        }  
        this.curpos = pos;  
        return true;  
    }