Java中的File操作总结
1.创建文件
import java.io.File;
import java.io.IOException;
public class CreateFileExample
{
public static void main( String[] args )
{
try {
File file = new File("c:\\newfile.txt");
//创建文件使用createNewFile()方法
if (file.createNewFile()){
System.out.println("File is created!");
}else{
System.out.println("File already exists.");
}
} catch (IOException e) {
e.printStackTrace();
}
}
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2.建立文件路径
import java.io.File;
import java.io.IOException;
public class FilePathExample1 {
public static void main(String[] args) {
try {
String filename = "newFile.txt";
String workingDirectory = System.getProperty("user.dir");
//****************//
String absoluteFilePath = "";
//absoluteFilePath = workingDirectory + System.getProperty("file.separator") + filename;
absoluteFilePath = workingDirectory + File.separator + filename;
System.out.println("Final filepath : " + absoluteFilePath);
//****************//
File file = new File(absoluteFilePath);
if (file.createNewFile()) {
System.out.println("File is created!");
} else {
System.out.println("File is already existed!");
}
} catch (IOException e) {
e.printStackTrace();
}
}
}
/////////////////////////////////////////////////////////////////
import java.io.File;
import java.io.IOException;
public class FilePathExample2 {
public static void main(String[] args) {
try {
String filename = "newFile.txt";
String workingDirectory = System.getProperty("user.dir");
//****************//
File file = new File(workingDirectory, filename);
//****************//
System.out.println("Final filepath : " + file.getAbsolutePath());
if (file.createNewFile()) {
System.out.println("File is created!");
} else {
System.out.println("File is already existed!");
}
} catch (IOException e) {
e.printStackTrace();
}
}
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3.设置文件权限
@检查文件权限是否设置
- file.canExecute()
- file.canWrite()
- file.canRead()
@设置权限
- file.setExecutable(boolean)
- file.setReadable(boolean)
- file.setWritable(boolean)
代码演示 ：
package com.File;
import java.io.File;
import java.io.IOException;
public class FilePermissionExample
{
public static void main( String[] args )
{
try {
//1.未设置权限
File file = new File("D:\\2.txt");
// if(file.exists()){
// System.out.println("是否可执行: " + file.canExecute());
// System.out.println("是否可写 : " + file.canWrite());
// System.out.println("是否可读 : " + file.canRead());
// }
//2.已设置权限
file.setExecutable(false);
file.setReadable(false);
file.setWritable(false);
System.out.println(" 是否可执行: " + file.canExecute());
System.out.println("是否可写 : " + file.canWrite());
System.out.println("是否可读 : " + file.canRead());
if (file.createNewFile()){
System.out.println("文件已创建!");
}else{
System.out.println("文件已存在");
}
} catch (IOException e) {
e.printStackTrace();
}
}
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4.读取文本内容的重要几个流
- BufferedInputStream
- FileInputStream
- FileReader
- BufferedReader
- FileInputStream
- DataInputStream
@.BufferedInputStream、 DataInputStream的使用
import java.io.BufferedInputStream;
import java.io.DataInputStream;
import java.io.File;
import java.io.FileInputStream;
import java.io.IOException;
public class BufferedInputStreamExample {
public static void main(String[] args) {
File file = new File("C:\\testing.txt");
FileInputStream fis = null;
BufferedInputStream bis = null;
DataInputStream dis = null;
try {
fis = new FileInputStream(file);
bis = new BufferedInputStream(fis);
dis = new DataInputStream(bis);
while (dis.available() != 0) {
System.out.println(dis.readLine());
}
} catch (IOException e) {
e.printStackTrace();
} finally {
try {
fis.close();
bis.close();
dis.close();
} catch (IOException ex) {
ex.printStackTrace();
}
}
}
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@ FileInputStream的使用
import java.io.File;
import java.io.FileInputStream;
import java.io.IOException;
public class ReadFileExample {
public static void main(String[] args) {
File file = new File("C:/robots.txt");
FileInputStream fis = null;
try {
fis = new FileInputStream(file);
System.out.println("Total file size to read (in bytes) : "
+ fis.available());
int content;
while ((content = fis.read()) != -1) {
// convert to char and display it
System.out.print((char) content);
}
} catch (IOException e) {
e.printStackTrace();
} finally {
try {
if (fis != null)
fis.close();
} catch (IOException ex) {
ex.printStackTrace();
}
}
}
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@BufferedReader的使用
import java.io.BufferedReader;
import java.io.FileReader;
import java.io.IOException;
public class ReadFileExample1 {
private static final String FILENAME = "E:\\test\\filename.txt";
public static void main(String[] args) {
BufferedReader br = null;
FileReader fr = null;
try {
//br = new BufferedReader(new FileReader(FILENAME));
fr = new FileReader(FILENAME);
br = new BufferedReader(fr);
String sCurrentLine;
while ((sCurrentLine = br.readLine()) != null) {
System.out.println(sCurrentLine);
}
} catch (IOException e) {
e.printStackTrace();
} finally {
try {
if (br != null)
br.close();
if (fr != null)
fr.close();
} catch (IOException ex) {
ex.printStackTrace();
}
}
}
}
#################################################################
import java.io.BufferedReader;
import java.io.FileReader;
import java.io.IOException;
public class ReadFileExample2 {
private static final String FILENAME = "E:\\test\\filename.txt";
public static void main(String[] args) {
try (BufferedReader br = new BufferedReader(new FileReader(FILENAME))) {
String sCurrentLine;
while ((sCurrentLine = br.readLine()) != null) {
System.out.println(sCurrentLine);
}
} catch (IOException e) {
e.printStackTrace();
}
}
}
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5.写入文本的几个重要的流
- BufferedOutputStream
- FileOutputStream
- FileWriter
- BufferedWriter
- FileOutputStream
- DataOutputStream
@FileOutputStream 的使用
import java.io.File;
import java.io.FileOutputStream;
import java.io.IOException;
public class WriteFileExample {
public static void main(String[] args) {
File file = new File("c:/newfile.txt");
String content = "This is the text content";
try (FileOutputStream fop = new FileOutputStream(file)) {
// if file doesn't exists, then create it
if (!file.exists()) {
file.createNewFile();
}
// get the content in bytes
byte[] contentInBytes = content.getBytes();
fop.write(contentInBytes);
fop.flush();
fop.close();
System.out.println("Done");
} catch (IOException e) {
e.printStackTrace();
}
}
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@BufferedWriter的使用
import java.io.BufferedWriter;
import java.io.FileWriter;
import java.io.IOException;
public class WriteToFileExample2 {
private static final String FILENAME = "E:\\test\\filename.txt";
public static void main(String[] args) {
try (BufferedWriter bw = new BufferedWriter(new FileWriter(FILENAME))) {
String content = "This is the content to write into file\n";
bw.write(content);
// no need to close it.
//bw.close();
System.out.println("Done");
} catch (IOException e) {
e.printStackTrace();
}
}
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6.向文件中添加新的内容
import java.io.BufferedWriter;
import java.io.File;
import java.io.FileWriter;
import java.io.IOException;
public class AppendToFileExample {
private static final String FILENAME = "E:\\test\\filename.txt";
public static void main(String[] args) {
BufferedWriter bw = null;
FileWriter fw = null;
try {
String data = " This is new content";
File file = new File(FILENAME);
// if file doesnt exists, then create it
if (!file.exists()) {
file.createNewFile();
}
// true = append file
fw = new FileWriter(file.getAbsoluteFile(), true);
bw = new BufferedWriter(fw);
bw.write(data);
System.out.println("Done");
} catch (IOException e) {
e.printStackTrace();
} finally {
try {
if (bw != null)
bw.close();
if (fw != null)
fw.close();
} catch (IOException ex) {
ex.printStackTrace();
}
}
}
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7.删除文件
mport java.io.File;
public class DeleteFileExample
{
public static void main(String[] args)
{
try{
File file = new File("c:\\logfile20100131.log");
if(file.delete()){
System.out.println(file.getName() + " is deleted!");
}else{
System.out.println("Delete operation is failed.");
}
}catch(Exception e){
e.printStackTrace();
}
}
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8.删除指定格式的所有文件
import java.io.*;
public class FileChecker {
private static final String FILE_DIR = "c:\\folder";
private static final String FILE_TEXT_EXT = ".txt";
public static void main(String args[]) {
new FileChecker().deleteFile(FILE_DIR,FILE_TEXT_EXT);
}
public void deleteFile(String folder, String ext){
GenericExtFilter filter = new GenericExtFilter(ext);
File dir = new File(folder);
//list out all the file name with .txt extension
String[] list = dir.list(filter);
if (list.length == 0) return;
File fileDelete;
for (String file : list){
String temp = new StringBuffer(FILE_DIR)
.append(File.separator)
.append(file).toString();
fileDelete = new File(temp);
boolean isdeleted = fileDelete.delete();
System.out.println("file : " + temp + " is deleted : " + isdeleted);
}
}
//inner class, generic extension filter
public class GenericExtFilter implements FilenameFilter {
private String ext;
public GenericExtFilter(String ext) {
this.ext = ext;
}
public boolean accept(File dir, String name) {
return (name.endsWith(ext));
}
}
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9.查找以某种格式的所有文件
import java.io.*;
public class FindCertainExtension {
private static final String FILE_DIR = "c:\\folder";
private static final String FILE_TEXT_EXT = ".jpg";
public static void main(String args[]) {
new FindCertainExtension().listFile(FILE_DIR, FILE_TEXT_EXT);
}
public void listFile(String folder, String ext) {
GenericExtFilter filter = new GenericExtFilter(ext);
File dir = new File(folder);
if(dir.isDirectory()==false){
System.out.println("Directory does not exists : " + FILE_DIR);
return;
}
// list out all the file name and filter by the extension
String[] list = dir.list(filter);
if (list.length == 0) {
System.out.println("no files end with : " + ext);
return;
}
for (String file : list) {
String temp = new StringBuffer(FILE_DIR).append(File.separator)
.append(file).toString();
System.out.println("file : " + temp);
}
}
// inner class, generic extension filter
public class GenericExtFilter implements FilenameFilter {
private String ext;
public GenericExtFilter(String ext) {
this.ext = ext;
}
public boolean accept(File dir, String name) {
return (name.endsWith(ext));
}
}
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10.修改文件名
import java.io.File;
public class RenameFileExample
{
public static void main(String[] args)
{
File oldfile =new File("oldfile.txt");
File newfile =new File("newfile.txt");
if(oldfile.renameTo(newfile)){
System.out.println("Rename succesful");
}else{
System.out.println("Rename failed");
}
}
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11.复制文件内容
import java.io.File;
import java.io.FileInputStream;
import java.io.FileOutputStream;
import java.io.IOException;
import java.io.InputStream;
import java.io.OutputStream;
public class CopyFileExample
{
public static void main(String[] args)
{
InputStream inStream = null;
OutputStream outStream = null;
try{
File afile =new File("Afile.txt");
File bfile =new File("Bfile.txt");
inStream = new FileInputStream(afile);
outStream = new FileOutputStream(bfile);
byte[] buffer = new byte[1024];
int length;
//copy the file content in bytes
while ((length = inStream.read(buffer)) > 0){
outStream.write(buffer, 0, length);
}
inStream.close();
outStream.close();
System.out.println("File is copied successful!");
}catch(IOException e){
e.printStackTrace();
}
}
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12.将一个文件移到另一个目录
import java.io.File;
public class MoveFileExample
{
public static void main(String[] args)
{
try{
File afile =new File("C:\\folderA\\Afile.txt");
if(afile.renameTo(new File("C:\\folderB\\" + afile.getName()))){
System.out.println("File is moved successful!");
}else{
System.out.println("File is failed to move!");
}
}catch(Exception e){
e.printStackTrace();
}
}
}
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13.创建文件是添加日期
import java.io.BufferedReader;
import java.io.IOException;
import java.io.InputStreamReader;
import java.util.StringTokenizer;
public class GetFileCreationDateExample
{
public static void main(String[] args)
{
try{
Process proc =
Runtime.getRuntime().exec("cmd /c dir c:\\logfile.log /tc");
BufferedReader br =
new BufferedReader(
new InputStreamReader(proc.getInputStream()));
String data ="";
//it's quite stupid but work
for(int i=0; i<6; i++){
data = br.readLine();
}
System.out.println("Extracted value : " + data);
//split by space
StringTokenizer st = new StringTokenizer(data);
String date = st.nextToken();//Get date
String time = st.nextToken();//Get time
System.out.println("Creation Date : " + date);
System.out.println("Creation Time : " + time);
}catch(IOException e){
e.printStackTrace();
}
}
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14.获取文件被修改的日期
import java.io.File;
import java.text.SimpleDateFormat;
public class GetFileLastModifiedExample
{
public static void main(String[] args)
{
File file = new File("c:\\logfile.log");
System.out.println("Before Format : " + file.lastModified());
SimpleDateFormat sdf = new SimpleDateFormat("MM/dd/yyyy HH:mm:ss");
System.out.println("After Format : " + sdf.format(file.lastModified()));
}
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15.修改文件日期
import java.io.File;
import java.text.ParseException;
import java.text.SimpleDateFormat;
import java.util.Date;
public class ChangeFileLastModifiedExample
{
public static void main(String[] args)
{
try{
File file = new File("C:\\logfile.log");
//print the original last modified date
SimpleDateFormat sdf = new SimpleDateFormat("MM/dd/yyyy");
System.out.println("Original Last Modified Date : "
+ sdf.format(file.lastModified()));
//set this date
String newLastModified = "01/31/1998";
//need convert the above date to milliseconds in long value
Date newDate = sdf.parse(newLastModified);
file.setLastModified(newDate.getTime());
//print the latest last modified date
System.out.println("Lastest Last Modified Date : "
+ sdf.format(file.lastModified()));
}catch(ParseException e){
e.printStackTrace();
}
}
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16.设置文件只能读
import java.io.File;
import java.io.IOException;
public class FileReadAttribute
{
public static void main(String[] args) throws IOException
{
File file = new File("c:/file.txt");
//mark this file as read only, since jdk 1.2
file.setReadOnly();
if(file.canWrite()){
System.out.println("This file is writable");
}else{
System.out.println("This file is read only");
}
//revert the operation, mark this file as writable, since jdk 1.6
file.setWritable(true);
if(file.canWrite()){
System.out.println("This file is writable");
}else{
System.out.println("This file is read only");
}
}
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17.获取文件大小
import java.io.File;
public class FileSizeExample
{
public static void main(String[] args)
{
File file =new File("c:\\java_xml_logo.jpg");
if(file.exists()){
double bytes = file.length();
double kilobytes = (bytes / 1024);
double megabytes = (kilobytes / 1024);
double gigabytes = (megabytes / 1024);
double terabytes = (gigabytes / 1024);
double petabytes = (terabytes / 1024);
double exabytes = (petabytes / 1024);
double zettabytes = (exabytes / 1024);
double yottabytes = (zettabytes / 1024);
System.out.println("bytes : " + bytes);
System.out.println("kilobytes : " + kilobytes);
System.out.println("megabytes : " + megabytes);
System.out.println("gigabytes : " + gigabytes);
System.out.println("terabytes : " + terabytes);
System.out.println("petabytes : " + petabytes);
System.out.println("exabytes : " + exabytes);
System.out.println("zettabytes : " + zettabytes);
System.out.println("yottabytes : " + yottabytes);
}else{
System.out.println("File does not exists!");
}
}
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18.获取文件路径
import java.io.File;
import java.io.IOException;
public class AbsoluteFilePathExample
{
public static void main(String[] args)
{
try{
File temp = File.createTempFile("i-am-a-temp-file", ".tmp" );
String absolutePath = temp.getAbsolutePath();
System.out.println("File path : " + absolutePath);
String filePath = absolutePath.
substring(0,absolutePath.lastIndexOf(File.separator));
System.out.println("File path : " + filePath);
}catch(IOException e){
e.printStackTrace();
}
}
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19.获取文件的总行数
import java.io.File;
import java.io.FileReader;
import java.io.IOException;
import java.io.LineNumberReader;
public class LineNumberReaderExample
{
public static void main(String[] args)
{
try{
File file =new File("c:\\ihave10lines.txt");
if(file.exists()){
FileReader fr = new FileReader(file);
LineNumberReader lnr = new LineNumberReader(fr);
int linenumber = 0;
while (lnr.readLine() != null){
linenumber++;
}
System.out.println("Total number of lines : " + linenumber);
lnr.close();
}else{
System.out.println("File does not exists!");
}
}catch(IOException e){
e.printStackTrace();
}
}
}
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20.检查文件是否存在
import java.io.*;
public class FileChecker {
public static void main(String args[]) {
File f = new File("c:\\mkyong.txt");
if(f.exists()){
System.out.println("File existed");
}else{
System.out.println("File not found!");
}
}
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21.检查 文件是否隐藏
import java.io.File;
import java.io.IOException;
public class FileHidden
{
public static void main(String[] args) throws IOException
{
File file = new File("c:/hidden-file.txt");
if(file.isHidden()){
System.out.println("This file is hidden");
}else{
System.out.println("This file is not hidden");
}
}
}- 1
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22.读取文件为UTF-8的数据
import java.io.BufferedReader;
import java.io.File;
import java.io.FileInputStream;
import java.io.IOException;
import java.io.InputStreamReader;
import java.io.UnsupportedEncodingException;
public class test {
public static void main(String[] args){
try {
File fileDir = new File("c:\\temp\\test.txt");
BufferedReader in = new BufferedReader(
new InputStreamReader(
new FileInputStream(fileDir), "UTF8"));
String str;
while ((str = in.readLine()) != null) {
System.out.println(str);
}
in.close();
}
catch (UnsupportedEncodingException e)
{
System.out.println(e.getMessage());
}
catch (IOException e)
{
System.out.println(e.getMessage());
}
catch (Exception e)
{
System.out.println(e.getMessage());
}
}
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23.向文件中写入UTF-8的数据
import java.io.BufferedWriter;
import java.io.File;
import java.io.FileOutputStream;
import java.io.IOException;
import java.io.OutputStreamWriter;
import java.io.UnsupportedEncodingException;
import java.io.Writer;
public class test {
public static void main(String[] args){
try {
File fileDir = new File("c:\\temp\\test.txt");
Writer out = new BufferedWriter(new OutputStreamWriter(
new FileOutputStream(fileDir), "UTF8"));
out.append("Website UTF-8").append("\r\n");
out.append("?? UTF-8").append("\r\n");
out.append("??????? UTF-8").append("\r\n");
out.flush();
out.close();
}
catch (UnsupportedEncodingException e)
{
System.out.println(e.getMessage());
}
catch (IOException e)
{
System.out.println(e.getMessage());
}
catch (Exception e)
{
System.out.println(e.getMessage());
}
}
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24.将 文本内容复制给一个变量
import java.io.DataInputStream;
import java.io.FileInputStream;
public class App{
public static void main (String args[]) {
try{
DataInputStream dis =
new DataInputStream (
new FileInputStream ("c:\\logging.log"));
byte[] datainBytes = new byte[dis.available()];
dis.readFully(datainBytes);
dis.close();
String content = new String(datainBytes, 0, datainBytes.length);
System.out.println(content);
}catch(Exception ex){
ex.printStackTrace();
}
}
}- 1
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25.生成文件校验值
import java.io.FileInputStream;
import java.security.MessageDigest;
public class TestCheckSum {
public static void main(String args[]) throws Exception {
String datafile = "c:\\INSTLOG.TXT";
MessageDigest md = MessageDigest.getInstance("SHA1");
FileInputStream fis = new FileInputStream(datafile);
byte[] dataBytes = new byte[1024];
int nread = 0;
while ((nread = fis.read(dataBytes)) != -1) {
md.update(dataBytes, 0, nread);
};
byte[] mdbytes = md.digest();
//convert the byte to hex format
StringBuffer sb = new StringBuffer("");
for (int i = 0; i < mdbytes.length; i++) {
sb.append(Integer.toString((mdbytes[i] & 0xff) + 0x100, 16).substring(1));
}
System.out.println("Digest(in hex format):: " + sb.toString());
}
}- 1
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26.将文件转换成字节数组
import java.io.File;
import java.io.FileInputStream;
import java.io.IOException;
import java.nio.file.Files;
import java.nio.file.Path;
import java.nio.file.Paths;
public class FileToArrayOfBytes {
public static void main(String[] args) {
try {
// convert file to byte[]
byte[] bFile = readBytesFromFile("C:\\temp\\testing1.txt");
//java nio
//byte[] bFile = Files.readAllBytes(new File("C:\\temp\\testing1.txt").toPath());
//byte[] bFile = Files.readAllBytes(Paths.get("C:\\temp\\testing1.txt"));
// save byte[] into a file
Path path = Paths.get("C:\temp\\test2.txt");
Files.write(path, bFile);
System.out.println("Done");
//Print bytes[]
for (int i = 0; i < bFile.length; i++) {
System.out.print((char) bFile[i]);
}
} catch (IOException e) {
e.printStackTrace();
}
}
private static byte[] readBytesFromFile(String filePath) {
FileInputStream fileInputStream = null;
byte[] bytesArray = null;
try {
File file = new File(filePath);
bytesArray = new byte[(int) file.length()];
//read file into bytes[]
fileInputStream = new FileInputStream(file);
fileInputStream.read(bytesArray);
} catch (IOException e) {
e.printStackTrace();
} finally {
if (fileInputStream != null) {
try {
fileInputStream.close();
} catch (IOException e) {
e.printStackTrace();
}
}
}
return bytesArray;
}
}- 1
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27.文件保存字节数组
import java.io.File;
import java.io.FileInputStream;
import java.io.FileOutputStream;
import java.io.IOException;
import java.nio.file.Files;
import java.nio.file.Path;
import java.nio.file.Paths;
public class ArrayOfBytesToFile {
private static final String UPLOAD_FOLDER = "C:\\temp\\";
public static void main(String[] args) {
FileInputStream fileInputStream = null;
try {
File file = new File("C:\\temp\\testing1.txt");
byte[] bFile = new byte[(int) file.length()];
//read file into bytes[]
fileInputStream = new FileInputStream(file);
fileInputStream.read(bFile);
//save bytes[] into a file
writeBytesToFile(bFile, UPLOAD_FOLDER + "test1.txt");
writeBytesToFileClassic(bFile, UPLOAD_FOLDER + "test2.txt");
writeBytesToFileNio(bFile, UPLOAD_FOLDER + "test3.txt");
System.out.println("Done");
} catch (IOException e) {
e.printStackTrace();
} finally {
if (fileInputStream != null) {
try {
fileInputStream.close();
} catch (IOException e) {
e.printStackTrace();
}
}
}
}
//Classic, < JDK7
private static void writeBytesToFileClassic(byte[] bFile, String fileDest) {
FileOutputStream fileOuputStream = null;
try {
fileOuputStream = new FileOutputStream(fileDest);
fileOuputStream.write(bFile);
} catch (IOException e) {
e.printStackTrace();
} finally {
if (fileOuputStream != null) {
try {
fileOuputStream.close();
} catch (IOException e) {
e.printStackTrace();
}
}
}
}
//Since JDK 7 - try resources
private static void writeBytesToFile(byte[] bFile, String fileDest) {
try (FileOutputStream fileOuputStream = new FileOutputStream(fileDest)) {
fileOuputStream.write(bFile);
} catch (IOException e) {
e.printStackTrace();
}
}
//Since JDK 7, NIO
private static void writeBytesToFileNio(byte[] bFile, String fileDest) {
try {
Path path = Paths.get(fileDest);
Files.write(path, bFile);
} catch (IOException e) {
e.printStackTrace();
}
}
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28.将字符串转换成InputStream
import java.io.BufferedReader;
import java.io.ByteArrayInputStream;
import java.io.IOException;
import java.io.InputStream;
import java.io.InputStreamReader;
public class StringToInputStreamExample {
public static void main(String[] args) throws IOException {
String str = "This is a String ~ GoGoGo";
// convert String into InputStream
InputStream is = new ByteArrayInputStream(str.getBytes());
// read it with BufferedReader
BufferedReader br = new BufferedReader(new InputStreamReader(is));
String line;
while ((line = br.readLine()) != null) {
System.out.println(line);
}
br.close();
}
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29.将InputStream转换为字符串
import java.io.BufferedReader;
import java.io.ByteArrayInputStream;
import java.io.IOException;
import java.io.InputStream;
import java.io.InputStreamReader;
public class InputStreamToStringExample {
public static void main(String[] args) throws IOException {
// intilize an InputStream
InputStream is =
new ByteArrayInputStream("file content..blah blah".getBytes());
String result = getStringFromInputStream(is);
System.out.println(result);
System.out.println("Done");
}
// convert InputStream to String
private static String getStringFromInputStream(InputStream is) {
BufferedReader br = null;
StringBuilder sb = new StringBuilder();
String line;
try {
br = new BufferedReader(new InputStreamReader(is));
while ((line = br.readLine()) != null) {
sb.append(line);
}
} catch (IOException e) {
e.printStackTrace();
} finally {
if (br != null) {
try {
br.close();
} catch (IOException e) {
e.printStackTrace();
}
}
}
return sb.toString();
}
}- 1
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30.将文件转换为十六进制
import java.io.File;
import java.io.FileInputStream;
import java.io.IOException;
import java.io.InputStream;
import java.io.PrintStream;
public class File2Hex
{
public static void convertToHex(PrintStream out, File file) throws IOException {
InputStream is = new FileInputStream(file);
int bytesCounter =0;
int value = 0;
StringBuilder sbHex = new StringBuilder();
StringBuilder sbText = new StringBuilder();
StringBuilder sbResult = new StringBuilder();
while ((value = is.read()) != -1) {
//convert to hex value with "X" formatter
sbHex.append(String.format("%02X ", value));
//If the chracater is not convertable, just print a dot symbol "."
if (!Character.isISOControl(value)) {
sbText.append((char)value);
}else {
sbText.append(".");
}
//if 16 bytes are read, reset the counter,
//clear the StringBuilder for formatting purpose only.
if(bytesCounter==15){
sbResult.append(sbHex).append(" ").append(sbText).append("\n");
sbHex.setLength(0);
sbText.setLength(0);
bytesCounter=0;
}else{
bytesCounter++;
}
}
//if still got content
if(bytesCounter!=0){
//add spaces more formatting purpose only
for(; bytesCounter<16; bytesCounter++){
//1 character 3 spaces
sbHex.append(" ");
}
sbResult.append(sbHex).append(" ").append(sbText).append("\n");
}
out.print(sbResult);
is.close();
}
public static void main(String[] args) throws IOException
{
//display output to console
convertToHex(System.out, new File("c:/file.txt"));
//write the output into a file
convertToHex(new PrintStream("c:/file.hex"), new File("c:/file.txt"));
}
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31.File如何得到空闲磁盘空间
import java.io.File;
public class DiskSpaceDetail
{
public static void main(String[] args)
{
File file = new File("c:");
long totalSpace = file.getTotalSpace(); //total disk space in bytes.
long usableSpace = file.getUsableSpace(); ///unallocated / free disk space in bytes.
long freeSpace = file.getFreeSpace(); //unallocated / free disk space in bytes.
System.out.println(" === Partition Detail ===");
System.out.println(" === bytes ===");
System.out.println("Total size : " + totalSpace + " bytes");
System.out.println("Space free : " + usableSpace + " bytes");
System.out.println("Space free : " + freeSpace + " bytes");
System.out.println(" === mega bytes ===");
System.out.println("Total size : " + totalSpace /1024 /1024 + " mb");
System.out.println("Space free : " + usableSpace /1024 /1024 + " mb");
System.out.println("Space free : " + freeSpace /1024 /1024 + " mb");
}
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https://blog.csdn.net/xiaodingqq/article/details/80093888
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