new 一个线程沲
打开文件，Nio或Reader，NIO打开，Map一大块MappedByteBuffer，从Buffer中读出一定大小的数据，定位到最后一个'\n'，最后一个'\n'及之前的数据put到一个线程执行类实例Buffer中，余下的put到一个临时Buffer里，下一次循环时处理这部分内容，在线程的执行体中，先行rewind bytebuffer，循环处理buffer，读到一个完整的import语句put到map里，buffer处理完成后合并map到全局concurrentmap中。BIO的则是读一定的行数后submit线程到线程沲，之后，用正则表达式处理每一行生成map，处理完成后合并map
上代码:
=========================NIO=================================
package com.arvey.files;
import java.io.File;
import java.io.FileInputStream;
import java.io.FileNotFoundException;
import java.io.IOException;
import java.nio.ByteBuffer;
import java.nio.MappedByteBuffer;
import java.nio.channels.FileChannel;
import java.util.ArrayList;
import java.util.Collections;
import java.util.Comparator;
import java.util.HashMap;
import java.util.List;
import java.util.Map;
import java.util.concurrent.ConcurrentHashMap;
import java.util.concurrent.ExecutorService;
import java.util.concurrent.Executors;
public class StateCounterNIO {
public static final int mappedSize = 5*4*1024;
public static final int handleSize = 4*1024;
public final static int ExecutorsNum = 200;
String file="/Users/arvey/wwork/Docs.code.clean/docsapp/bigfile.src";
//String file="/Users/arvey/wwork/Docs.full/source.code.201512.clean/bigfile.src";
//String file="/Users/arvey/wwork/gsafety.code.donotdeleted/cloud-core/bigfile.src";
//String file="/Users/arvey/wwork/Docs.full/source.code.201512.clean/CleanerType.java";
public static ConcurrentHashMap<String,Integer> result = new ConcurrentHashMap<String,Integer>();
//public static Pattern pattern = Pattern.compile("^(import.+);");
private ExecutorService pool = Executors.newFixedThreadPool(ExecutorsNum);
//private HandleBuffer aHandle;
public static synchronized void updateTopList(Map<String,Integer> partial){
for(String key:partial.keySet()){
if(result.containsKey(key)){
result.put(key, (Integer)result.get(key)+(Integer)partial.get(key));
}else
result.put(key, (Integer)partial.get(key));
}
}
public void getTop10(){
File aFile = new File(file);
long fileLength = aFile.length();
FileInputStream fis = null;
FileChannel fc = null;
long foffset = 0L;
//MappedByteBuffer buffer = (MappedByteBuffer) MappedByteBuffer.allocate(5*4*1024);
MappedByteBuffer buffer = null;
ByteBuffer tmpByteBuffer = ByteBuffer.allocate(StateCounterNIO.handleSize);
byte[] tmpByteArray = new byte[StateCounterNIO.handleSize];
try {
fis = new FileInputStream(aFile);
fc = fis.getChannel();
while(foffset<fileLength){
long buffersize = Math.min(fileLength-foffset,StateCounterNIO.mappedSize);
buffer = fc.map(FileChannel.MapMode.READ_ONLY, foffset, buffersize);
while( buffer.position() < buffersize ){
HandleBuffer aHandle = new HandleBuffer();
//boolean submit = false;
if(tmpByteBuffer.position() > 0){
byte[] tmpba = new byte[tmpByteBuffer.position()];
tmpByteBuffer.rewind();
tmpByteBuffer.get(tmpba);
aHandle.getMbuffer().put(tmpba);
tmpByteBuffer.clear();
}
int tmpBACap = Math.min(Math.min(StateCounterNIO.handleSize, (int)(buffersize - buffer.position())), StateCounterNIO.handleSize - aHandle.getMbuffer().position() );
buffer.get(tmpByteArray,0,tmpBACap);
//end of file
if(buffer.position() == buffersize && (foffset+buffersize == fileLength)){
aHandle.getMbuffer().put(tmpByteArray,0,tmpBACap);
} else {
for( int i = tmpBACap-1;i>=0;i-- ){
if(i == 0){//this means that no '\n' in the whole buffer, then put full handle buffer and submit
tmpByteBuffer.put(tmpByteArray,0,tmpBACap);
}
if ( tmpByteArray[i] == '\n'){
aHandle.getMbuffer().put(tmpByteArray, 0, i);
//put those byte into tmpByteBuffer which will handle with next buffer
if( i != tmpBACap-1 )
tmpByteBuffer.put(tmpByteArray,i,tmpBACap-i);
break;
}
}
}
pool.submit( aHandle );
}
foffset += buffer.position();
buffer.clear();
}
//if(pool.
} catch (FileNotFoundException e) {
// TODO Auto-generated catch block
e.printStackTrace();
} catch (IOException e) {
// TODO Auto-generated catch block
e.printStackTrace();
} finally {
if (fis != null)
try {
fis.close();
} catch (IOException e) {
// TODO Auto-generated catch block
e.printStackTrace();
}
if( fc != null )
try {
fc.close();
} catch (IOException e) {
// TODO Auto-generated catch block
e.printStackTrace();
}
}
pool.shutdown();
while(!pool.isTerminated()){
try {
Thread.sleep(2000);
} catch (InterruptedException e) {
// TODO Auto-generated catch block
e.printStackTrace();
}
}
}
class HandleBuffer implements Runnable{
ByteBuffer mbuffer = ByteBuffer.allocate(4*1024);
public ByteBuffer getMbuffer(){
return mbuffer;
}
@Override
public void run() {
Map<String,Integer> aMap = new HashMap<String,Integer>();
byte[] bimport = "import ".getBytes();
int bimport_index = 0,markedpos = 0;
boolean isImportline = false;
int availabesize = mbuffer.position();
mbuffer.rewind();
while(mbuffer.position() < availabesize)
{
//mbuffer.
byte abyte = mbuffer.get();
if(!isImportline && bimport_index< bimport.length && abyte == bimport[bimport_index] ){
bimport_index++;
if( bimport_index == bimport.length ){
isImportline = true;
markedpos = mbuffer.position() - bimport.length;
}
}
else if( abyte == '\n' && isImportline){
byte[] tmp = new byte[mbuffer.position() - markedpos];
mbuffer.position(markedpos);
mbuffer.get(tmp);
String aImport = new String( tmp ).trim();
if(aMap.containsKey(aImport)){
aMap.put(aImport, (Integer)aMap.get(aImport)+1);
}else{
aMap.put(aImport, 1);
}
isImportline = false;
bimport_index=0;
} else if(!isImportline && bimport_index != 0){//清除没有读到完整"import "时的index
bimport_index = 0;
}
}
StateCounterNIO.updateTopList(aMap);
}
}
public static void main(String[] args) {
// TODO Auto-generated method stub
long startat = System.currentTimeMillis();
StateCounterNIO aNIO = new StateCounterNIO();
aNIO.getTop10();
List<Map.Entry<String,Integer>> slist = new ArrayList<Map.Entry<String,Integer>>(result.entrySet());
Collections.sort(slist,new Comparator<Map.Entry<String,Integer>>(){
@Override
public int compare(Map.Entry<String, Integer> o1, Map.Entry<String, Integer> o2) {
if(o2.getValue()!=null&&o1.getValue()!=null&&o2.getValue().compareTo(o1.getValue())>0){
return 1;
}else{
return -1;
}
}
});
int index=0;
for(Map.Entry<String,Integer> aEntry: slist){
System.out.println(aEntry.getKey() + "--"+ aEntry.getValue());
if(index++>=100)
break;
}
//System.out.println("The Thread counter is " + aCount.getPoolcounter());
System.out.println("The cost is " + (System.currentTimeMillis()-startat) );
}
}
==================================BIO======================================效率分析
处理大文件 文件size达到8967006720时 线程沲200 100 50对比如下（五次执行平均结果）：
NIO BIO
200 139843 67376
100 136914 66576
50 140000 67249
为何NIO的要慢于BIO的呢？
NIO在处理线程中遍例buffer，是不是这个原因造成的呢？当增加每次buffer处理的容量时，性能提升明显，如文件每次map的和每一个线程处理的buffer的空间扩容10增时，在50个线程时，数据降到82439，但是对于BIO的调整一次处理的行数，性能变化很小，程序运行时间略有增长（726**），then什么才能获得最好的性能呢！