package com.myjava;
import java.io.*;
import java.util.ArrayList;
import java.util.Collections;
import java.util.List;
/**
* Created by 14061371 on 2017/5/12.
*/
public class FileUtils {
//获取当前路径
/** 按字节读取
*
* @param fileName
*/
public static void readFileByBytes(String fileName){
File file=new File(fileName);
if(!file.exists()){
return;
}
InputStream in = null;
try {
in = new FileInputStream(file);
byte[] tempbytes = new byte[100];
int byteread = 0;
in = new FileInputStream(fileName);
// 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 (IOException e) {
e.printStackTrace();
}finally {
if (in != null) {
try {
in.close();
} catch (IOException e1) {
}
}
}
}
/**
* 按字符读取
* @param fileName
*/
public static void readFileByChars(String fileName){
File file=new File(fileName);
if(!file.exists()){
return;
}
Reader reader=null;
try {
reader=new InputStreamReader(new FileInputStream(file));
int tempChart;
char[] tempchars = new char[30];
while((tempChart=reader.read(tempchars))!=-1){
System.out.print(tempchars);
}
} catch (IOException e) {
e.printStackTrace();
}finally{
if(reader!=null){
try{
reader.close();
}catch (IOException e){
}
}
}
}
/**
* 按行读取
* @param fileName
*/
public static void readFileByLines(String fileName){
File file=new File(fileName);
if(!file.exists()){
return;
}
BufferedReader reader=null;
try {
reader=new BufferedReader(new FileReader(file));
String tempString=null;
int line=1;
while((tempString=reader.readLine())!=null){
System.out.println(line+tempString);
line++;
}
reader.close();
} catch (IOException e) {
e.printStackTrace();
}finally{
if(reader!=null){
try{
reader.close();
}catch(IOException e){
}
}
}
}
/**
* random读取文件
* @param fileName
*/
public static void readFileByRandomAccess(String fileName){
RandomAccessFile randomFile=null;
try {
randomFile=new RandomAccessFile(fileName,"r");
long fileLength=randomFile.length();
randomFile.seek(0);
byte[] bytes=new byte[10];
int byteread=0;
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 e) {
}
}
}
}
/**
* 读取文件最后N行
*
* 根据换行符判断当前的行数，
* 使用统计来判断当前读取第N行
*
* PS:输出的List是倒叙，需要对List反转输出
*
* @param file 待文件
* @param numRead 读取的行数
* @return List<String>
*/
public static List<String> readLastNLine(File file, long numRead) {
// 定义结果集
List<String> result = new ArrayList<String>();
//行数统计
long count = 0;
// 排除不可读状态
if (!file.exists() || file.isDirectory() || !file.canRead()) {
return null;
}
// 使用随机读取
RandomAccessFile fileRead = null;
try {
//使用读模式
fileRead = new RandomAccessFile(file, "r");
//读取文件长度
long length = fileRead.length();
//如果是0，代表是空文件，直接返回空结果
if (length == 0L) {
return result;
} else {
//初始化游标
long pos = length - 1;
while (pos > 0) {
pos--;
//开始读取
fileRead.seek(pos);
//如果读取到\n代表是读取到一行
if (fileRead.readByte() == '\n') {
//使用readLine获取当前行
String line = fileRead.readLine();
//保存结果
result.add(line);
//打印当前行
// System.out.println(line);
//行数统计，如果到达了numRead指定的行数，就跳出循环
count++;
if (count == numRead) {
break;
}
}
}
if (pos == 0) {
fileRead.seek(0);
result.add(fileRead.readLine());
}
}
} catch (IOException e) {
e.printStackTrace();
} finally {
if (fileRead != null) {
try {
//关闭资源
fileRead.close();
} catch (Exception e) {
}
}
}
Collections.reverse(result);
return result;
}
/**
* 使用RandomAccessFile追加文件
* @param fileName
*/
public static void appendFileByAccess(String fileName,String content){
try {
RandomAccessFile randomFile=new RandomAccessFile(fileName,"rw");
long fileLength=randomFile.length();
randomFile.seek(fileLength);
randomFile.writeBytes(content);
randomFile.close();
} catch (IOException e) {
e.printStackTrace();
}
}
/**
* 使用FileWriter 追加文件内容
* @param fileName
* @param content
*/
public static void appendFile(String fileName,String content){
try {
FileWriter writer=new FileWriter(fileName,true);
writer.write(content);
writer.close();
} catch (IOException e) {
e.printStackTrace();
}
}
/**
* 往文件头插入数据
* @param filename
* @param pos
* @param insertContent
*/
public static void insert(String filename, int pos, String insertContent){
RandomAccessFile raf=null;
FileOutputStream tmpOut=null;
FileInputStream tmpIn=null;
try{
File tmp = File.createTempFile("tmp", null);
tmp.deleteOnExit();
raf = new RandomAccessFile(filename, "rw");
tmpOut = new FileOutputStream(tmp);
tmpIn = new FileInputStream(tmp);
raf.seek(pos);//首先的话是0
byte[] buf = new byte[64];
int hasRead = 0;
while ((hasRead = raf.read(buf)) > 0) {
//把原有内容读入临时文件
tmpOut.write(buf, 0, hasRead);
}
raf.seek(pos);
raf.write(insertContent.getBytes());
//追加临时文件的内容
while ((hasRead = tmpIn.read(buf)) > 0) {
raf.write(buf, 0, hasRead);
}
}catch (IOException e) {
e.printStackTrace();
}finally{
try {
if (raf != null) {
raf.close();
}
if (tmpOut != null) {
tmpOut.close();
}
if (tmpIn != null) {
tmpIn.close();
}
} catch (IOException e) {
}
}
}
}
