nio按行读文件

不废话，直接上代码

package com.syz.test.nio;import java.io.IOException;import java.io.RandomAccessFile;import java.nio.ByteBuffer;import java.nio.channels.FileChannel;public class DataReader {    /**     * 按行读，行的分隔符必须是单个字符"\n"     */    public static void readByLine(String filePath,String encoding,int bufferSize) {        byte lf = 10;//"\n"        RandomAccessFile raf = null;        FileChannel fc = null;        try {            raf = new RandomAccessFile(filePath, "r");            fc = raf.getChannel();            ByteBuffer buffer = ByteBuffer.allocate(bufferSize);            //保存换行后未处理的数据            byte[] temp = new byte[0];            while (fc.read(buffer)!= -1) {                int position = buffer.position();// 读取结束后的位置，相当于读取的长度                byte[] bs = new byte[position];// 用来存放读取的内容的数组                buffer.rewind();// 将position设回0,所以你可以重读Buffer中的所有数据,此处如果不设置,无法使用下面的get方法                buffer.get(bs);// 相当于buffer.get(bs,0,bs.length())：从position初始位置开始相对读,读bs.length个byte,并写入bs[0]到bs[bs.length-1]的区域                buffer.clear();                //要加上上次未处理的数据                int readSize = position + temp.length;                byte[] readByte = new byte[readSize];                System.arraycopy(temp, 0, readByte, 0, temp.length);                System.arraycopy(bs, 0, readByte, temp.length, position);                int start = 0;                int lineByteSize = 0;                byte[] lineByte = new byte[0];                for (int i = 0; i < readSize; i++) {                    if (readByte[i] == lf) {                        lineByte = new byte[lineByteSize];                        System.arraycopy(readByte, start, lineByte, 0, lineByteSize);                        String lineStr = new String(lineByte, encoding);                        System.out.println(lineStr);                        lineByteSize=0;                        start = i+1;                    } else {                        lineByteSize++;                    }                }                // 把剩余的放入临时数组中                temp = new byte[lineByteSize];                System.arraycopy(readByte, start, temp, 0, lineByteSize);            }            //处理临时数组中的数据            if(temp.length>0){                String lineStr = new String(temp, encoding);                System.out.println(lineStr);            }        } catch (Exception e) {            e.printStackTrace();        } finally {            if (fc != null) {                try {                    fc.close();                } catch (IOException e) {                    e.printStackTrace();                }            }            if (raf != null) {                try {                    raf.close();                } catch (IOException e) {                    e.printStackTrace();                }            }        }    }    /**     * 按条读     * 举例：abc\ndef     * 分隔符可以是多个字符，如：abc\n\rdedf     * 如果设置成\n，就是按行读了     * @param filePath 文件路径     * @param encoding 字符集     * @param bufferSize 每次读多少字节     * @param itemSplit 第条的分隔符     */    public static void readByItem(String filePath,String encoding,int bufferSize,String itemSplit) {        RandomAccessFile raf = null;        FileChannel fc = null;        try {            raf = new RandomAccessFile(filePath, "r");            fc = raf.getChannel();            ByteBuffer buffer = ByteBuffer.allocate(bufferSize);            byte[] itemSplitByte = itemSplit.getBytes(encoding);            int itemSplitLen = itemSplitByte.length;            //保存未处理的数据            byte[] temp = new byte[0];            int itemIndex = 0;            while (fc.read(buffer)!= -1) {                int position = buffer.position();// 读取结束后的位置，相当于读取的长度                byte[] bs = new byte[position];// 用来存放读取的内容的数组                buffer.rewind();// 将position设回0,所以你可以重读Buffer中的所有数据,此处如果不设置,无法使用下面的get方法                buffer.get(bs);// 相当于buffer.get(bs,0,bs.length())：从position初始位置开始相对读,读bs.length个byte,并写入bs[0]到bs[bs.length-1]的区域                buffer.clear();                //要加上上次未处理的数据                int readSize = position + temp.length;                byte[] readByte = new byte[readSize];                System.arraycopy(temp, 0, readByte, 0, temp.length);                System.arraycopy(bs, 0, readByte, temp.length, position);                int start = 0;                int columnByteSize = 0;                byte[] columnByte = new byte[0];                int itemSplitIndex = 0;                for (int i = 0; i < readSize; i++) {                    columnByteSize++;                    if (readByte[i] == itemSplitByte[itemSplitIndex]) {                        itemSplitIndex++;                        if(itemSplitIndex==itemSplitLen){                            columnByteSize = columnByteSize-itemSplitLen;                            columnByte = new byte[columnByteSize];                            System.arraycopy(readByte, start, columnByte, 0, columnByteSize);                            String column = new String(columnByte, encoding);                            System.out.println(itemIndex+"\t"+column);                            itemIndex++;                            start = i + 1;                            columnByteSize = 0;                            itemSplitIndex = 0;                        }                    } else {                        itemSplitIndex=0;                    }                }                // 把剩余的放入临时数组中                temp = new byte[columnByteSize];                System.arraycopy(readByte, start, temp, 0, columnByteSize);            }            //处理临时数组中的数据            System.out.println("temp.length="+temp.length);            if(temp.length>0){                String column = new String(temp, encoding);                System.out.println(itemIndex+"\t"+column);            }        } catch (Exception e) {            e.printStackTrace();        } finally {            if (fc != null) {                try {                    fc.close();                } catch (IOException e) {                    e.printStackTrace();                }            }            if (raf != null) {                try {                    raf.close();                } catch (IOException e) {                    e.printStackTrace();                }            }        }    }    /**     * 按条读，每一条又有被分成若干个列     * 举例：a|b|\nc|d\n     * 分隔符可以是多个字符，如：a::b::c\n\rd::e::f\n\r     * 严重声明：条分隔符与列分隔符不能有一样的符号，如columnSplit=|,itemSplit=||，它们都有|符号。     * 因为这个是逐个读的，不太好区分读到||的第一个字符时要不要切分列     * @param filePath 文件路径     * @param encoding 字符集     * @param bufferSize 每次读多少字节     * @param itemSplit 第条的分隔符     * @param columnSplit 每条中每列的分隔符     */    public static void readByItem(String filePath,String encoding,int bufferSize,String itemSplit,String columnSplit) {        RandomAccessFile raf = null;        FileChannel fc = null;        try {            raf = new RandomAccessFile(filePath, "r");            fc = raf.getChannel();            ByteBuffer buffer = ByteBuffer.allocate(bufferSize);            byte[] columnSplitByte = columnSplit.getBytes(encoding);            int columnSplitLen = columnSplitByte.length;            byte[] itemSplitByte = itemSplit.getBytes(encoding);            int itemSplitLen = itemSplitByte.length;            //保存未处理的数据            byte[] temp = new byte[0];            int columnIndex = 0;            int itemIndex = 0;            while (fc.read(buffer)!= -1) {                int position = buffer.position();// 读取结束后的位置，相当于读取的长度                byte[] bs = new byte[position];// 用来存放读取的内容的数组                buffer.rewind();// 将position设回0,所以你可以重读Buffer中的所有数据,此处如果不设置,无法使用下面的get方法                buffer.get(bs);// 相当于buffer.get(bs,0,bs.length())：从position初始位置开始相对读,读bs.length个byte,并写入bs[0]到bs[bs.length-1]的区域                buffer.clear();                //要加上上次未处理的数据                int readSize = position + temp.length;                byte[] readByte = new byte[readSize];                System.arraycopy(temp, 0, readByte, 0, temp.length);                System.arraycopy(bs, 0, readByte, temp.length, position);                int start = 0;                int columnByteSize = 0;                byte[] columnByte = new byte[0];                int columnSplitIndex = 0;                int itemSplitIndex = 0;                for (int i = 0; i < readSize; i++) {                    columnByteSize++;                    if (readByte[i] == columnSplitByte[columnSplitIndex]) {                        columnSplitIndex++;                        if(columnSplitIndex==columnSplitLen){                            columnByteSize = columnByteSize-columnSplitLen;                            columnByte = new byte[columnByteSize];                            System.arraycopy(readByte, start, columnByte, 0, columnByteSize);                            String column = new String(columnByte, encoding);                            System.out.println(columnIndex+"\t"+column);                            columnIndex++;                            start = i + 1;                            columnByteSize = 0;                            columnSplitIndex = 0;                        }                    } else {                        columnSplitIndex = 0;                    }                    if (readByte[i] == itemSplitByte[itemSplitIndex]) {                        itemSplitIndex++;                        if(itemSplitIndex==itemSplitLen){                            columnByteSize = columnByteSize-itemSplitLen;                            columnByte = new byte[columnByteSize];                            System.arraycopy(readByte, start, columnByte, 0, columnByteSize);                            String column = new String(columnByte, encoding);                            System.out.println(columnIndex+"\t"+column);                            System.out.println(itemIndex+"==========");                            columnIndex=0;                            itemIndex++;                            start = i + 1;                            columnByteSize = 0;                            itemSplitIndex = 0;                        }                    } else {                        itemSplitIndex=0;                    }                }                // 把剩余的放入临时数组中                temp = new byte[columnByteSize];                System.arraycopy(readByte, start, temp, 0, columnByteSize);            }            //处理临时数组中的数据            System.out.println("temp.length="+temp.length);            if(temp.length>0){                String column = new String(temp, encoding);                System.out.println(columnIndex+"\t"+column);            }        } catch (Exception e) {            e.printStackTrace();        } finally {            if (fc != null) {                try {                    fc.close();                } catch (IOException e) {                    e.printStackTrace();                }            }            if (raf != null) {                try {                    raf.close();                } catch (IOException e) {                    e.printStackTrace();                }            }        }    }    public static void main(String[] args) {        long t1 = System.currentTimeMillis();        String columnSplit = "|";        String itemSplit = "\n";        int bufferSize = 48;        String encoding = "GBK";        String filePath = "d:/data/a1.txt";        //readByLine(filePath,encoding,bufferSize);        //readByItem(filePath,encoding,bufferSize,itemSplit);        readByItem(filePath,encoding,bufferSize,itemSplit,columnSplit);        long t2 = System.currentTimeMillis();        System.out.println("time==="+(t2-t1));    }}

写文件

package com.syz.test.nio;import java.io.IOException;import java.io.RandomAccessFile;import java.nio.ByteBuffer;import java.nio.channels.FileChannel;import java.text.SimpleDateFormat;import java.util.Date;public class DataWriter {    public static void main(String[] args) {        long t1 = System.currentTimeMillis();        write();        long t2 = System.currentTimeMillis();        System.out.println("time==="+(t2-t1));    }    public static void write() {        SimpleDateFormat sdf = new SimpleDateFormat("yyyyMMddHHmmss");        String date = sdf.format(new Date());        StringBuffer sb = new StringBuffer();        int bufferSize = 1024;        String encoding = "UTF-8";        String filePath = "d:/data/a_"+date+".txt";        RandomAccessFile raf = null;        FileChannel fc = null;        try {            raf = new RandomAccessFile(filePath, "rws");            fc = raf.getChannel();            ByteBuffer buffer = ByteBuffer.allocate(bufferSize);            int count = 0;            for(int i=0;i<10;i++){                sb = new StringBuffer();                sb.append("20170410_"+i);                sb.append("|");                sb.append("127.0.0.1");                sb.append("|");                sb.append("测试中文");                sb.append("|");                sb.append("www.xxx.com"+date+"_"+i);                sb.append("|");                sb.append("");                sb.append("|");                sb.append("");                sb.append("|");                sb.append("测试中文222abc");                sb.append("|");                sb.append("测ha");                sb.append("|");                sb.append("");                sb.append("|");                sb.append("2017-03-02");                sb.append("|");                sb.append("2017-03-02");                sb.append("|");                sb.append("2017-03-02");                sb.append("|");                sb.append("22haa测试");                sb.append("|");                sb.append("abc123");                sb.append("\n");                String data = sb.toString();                byte[] dataByte = data.getBytes(encoding);                int dataLen = dataByte.length;                for(int j=0;j<dataLen;j++){                    if(count==bufferSize){                        buffer.flip();                        int a  = fc.write(buffer);                        System.out.println("a="+a);                        buffer.clear();                        count=0;                    }                    buffer.put(dataByte[j]);                    count ++;                }            }            buffer.flip();            //写入最后一点儿            int b = fc.write(buffer);            System.out.println("b="+b);        } catch (Exception e) {            e.printStackTrace();        }finally{            if(fc!=null){                try {                    fc.close();                } catch (IOException e) {                    e.printStackTrace();                }            }            if(raf!=null){                try {                    raf.close();                } catch (IOException e) {                    e.printStackTrace();                }            }        }    }}