public static void readTxt(String filePath) {
try {
File file = new File(filePath);
if(file.isFile() && file.exists()) {
InputStreamReader isr = new InputStreamReader(new FileInputStream(file), "utf-8");
BufferedReader br = new BufferedReader(isr);
String lineTxt = null;
int num =0;
long time1 = System.currentTimeMillis();
while ((lineTxt = br.readLine()) != null) {
System.out.println(lineTxt);
num++;
System.out.println("总共"+num+"条数据！");
}
//System.out.println("总共"+num+"条数据！");
long time2 = System.currentTimeMillis();
long time = time1 - time2;
System.out.println("共花费"+time+"秒");
br.close();
} else {
System.out.println("文件不存在!");
}
} catch (Exception e) {
System.out.println("文件读取错误!");
}
}
public static void main(String[] args) {
String filePath = "/Users/work/name.txt";
System.out.println(filePath);
readTxt(filePath);
}
Java NIO(New IO)是一个能够替代标准Java IO API的IO API（从Java 1.4开始)，Java NIO提供了与标准IO不一样的IO工做方式。
经测试，速度比流的方式耗时少一半时间；
博客连接：http://ifeve.com/java-nio-all/html
public static void readTxtByNIO(String filePath) {
long time1 = System.currentTimeMillis();
FileInputStream fis = null;
FileChannel inChannel = null;
int bufSize = 1024*10;
try {
fis = new FileInputStream(filePath);
inChannel = fis.getChannel();
System.out.println("file size --->"+inChannel.size());
ByteBuffer buffer = ByteBuffer.allocate(bufSize);
// System.out.println("buffer init position --->"+buffer.position()+"---- buffer init remaining --->"+buffer.remaining());
//这里标记了后面才能够调用buffer.reset(), 并且只能调用一次,
//否则会抛出java.nio.InvalidMarkException
//buffer.mark();
String enterStr = "\n";
StringBuffer strBuf = new StringBuffer("");
int lineNum = 0;
while(inChannel.read(buffer) != -1){
int rSize = buffer.position();
buffer.clear();
String tempString = new String(buffer.array(), 0, rSize);
if(fis.available() ==0){//最后一行，加入"\n分割符"
tempString+="\n";
}
int fromIndex = 0;
int endIndex = 0;
while ((endIndex = tempString.indexOf(enterStr, fromIndex)) != -1) {
String line = tempString.substring(fromIndex, endIndex);
line = new String(strBuf.toString() + line);
System.out.println(line);
strBuf.delete(0, strBuf.length());
fromIndex = endIndex + 1;
lineNum++;
}
if (rSize > tempString.length()) {
strBuf.append(tempString.substring(fromIndex, tempString.length()));
} else {
strBuf.append(tempString.substring(fromIndex, rSize));
}
System.out.println("lineNum ="+ lineNum);
}
} catch (Exception e) {
System.out.println("文件读取错误!");
} finally {
if(fis != null){
try {
fis.close();
} catch (IOException e) {
e.printStackTrace();
}
}
if(inChannel != null){
try{
inChannel.close();
}catch (IOException e){
e.printStackTrace();
}
}
long time2 = System.currentTimeMillis();
long time = (time1-time2)/1000;
System.out.println("共花费"+time+"秒");
}
}
public static void main(String[] args) {
String filePath = "/Users/work/name.txt";
System.out.println(filePath);
readTxtByBuffer(filePath);
//readTxtByNIO(filePath);
}
博客连接：https://www.cnblogs.com/lyftest/p/6564282.htmljava
package test;
import java.io.*;
import java.nio.ByteBuffer;
import java.nio.MappedByteBuffer;
import java.nio.channels.FileChannel;
import java.util.List;
/** * Created by qxr4383 on 2018/3/9. */
public class importTest2 {
public static void main(String[] args) {
String filePath = "/Users/qxr4383/Documents/work/logger/prod/id5/id5-weather/2018/weather.txt";
String filePath1 = "/Users/qxr4383/Documents/work/logger/prod/access/2018/01/1.txt";
System.out.println(filePath1);
readTxt(filePath);
}
static int length = 0x8000000; // 128 Mb
public static void readTxt(String filePath){
long timeStar = System.currentTimeMillis();// 获得当前的时间
// FileInputStream fis = null;
// FileChannel inChannel = null;
// int bufSize = 1024 * 14 * 1024;
File file = new File(filePath);
importTest2 mf = new importTest2();
try {
mf.structXML(file);
// fis = new FileInputStream(filePath);
// inChannel = fis.getChannel();
// ByteBuffer buffer = ByteBuffer.allocate(bufSize);
// MappedByteBuffer mbb = inChannel.map(FileChannel.MapMode.READ_ONLY, 0, inChannel.size());
// new Thread(new CompareThread(buffer)).start();
// for (int i = 0; i < length; i++) {
// mbb.put((byte) 'x');
// }
// System.out.println("Finished writing");
// //读取文件中间6个字节内容
// for (int i = length / 2; i < length / 2 + 6; i++) {
// System.out.print((char) mbb.get(i));
// }
} catch (Exception e) {
System.out.println("文件读取错误!");
e.printStackTrace();
} finally {
// if(fis != null){
// try {
// fis.close();
// } catch (IOException e) {
// e.printStackTrace();
// }
// }
// if(inChannel != null){
// try{
// inChannel.close();
// }catch (IOException e){
// e.printStackTrace();
// }
// }
long timeEnd = System.currentTimeMillis();
long time = (timeEnd-timeStar);
System.out.println("共花费"+time+"ms");
}
}
private List structXML(File file) throws IOException{
// for(int i=1;i<=8;i++){
try {
if(file.length()<length){
length = (int)file.length();
}
MappedByteBuffer buffer = new RandomAccessFile(file, "r")
.getChannel().map(FileChannel.MapMode.READ_ONLY,
// file.length()*7/8,file.length()/8);
0, length);
new Thread(new CompareThread(buffer)).start();
} catch (FileNotFoundException e) {
e.printStackTrace();
} catch (IOException e) {
e.printStackTrace();
}
// }
return null;
}
class CompareThread implements Runnable{
private MappedByteBuffer buffer = null;
final int BUFFER_SIZE = 0x1000;
byte[] dst = new byte[BUFFER_SIZE];
public CompareThread(MappedByteBuffer buffer) {
this.buffer = buffer;
// this.length = length;
}
public void run(){
long start = System.currentTimeMillis();
String enterStr = "\n";
StringBuffer strBuf = new StringBuffer("");
long total=0;
for (int offset = 0; offset < this.buffer.capacity(); offset += BUFFER_SIZE) {
if (this.buffer.capacity() - offset >= BUFFER_SIZE) {
for (int i = 0; i < BUFFER_SIZE; i++)
dst[i] = this.buffer.get(offset + i);
} else {
for (int i = 0; i < this.buffer.capacity() - offset; i++)
dst[i] = this.buffer.get(offset + i);
}
int length = (this.buffer.capacity() % BUFFER_SIZE == 0) ? BUFFER_SIZE
: this.buffer.capacity() % BUFFER_SIZE;
String tempString = new String(dst, 0, length);
int fromIndex = 0;
int endIndex = 0;
while ((endIndex = tempString.indexOf(enterStr, fromIndex)) != -1) {
total++;
String line = tempString.substring(fromIndex, endIndex);
line = new String(strBuf.toString() + line);
//System.out.println(line);
fromIndex = endIndex + 1;
strBuf.delete(0, strBuf.length());
}
// if (rSize > tempString.length()) {
// strBuf.append(tempString.substring(fromIndex,tempString.length()));
// } else {
// strBuf.append(tempString.substring(fromIndex, rSize));
// }
}
System.out.println("total----->"+total+"====耗时==="+(System.currentTimeMillis()-start));
}
}
}