Java之文件流(26个Demo)
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Java文件流主要包括字节流和字符流，字符流本质上就是字节流+编码表，下面通过26个案例介绍了字符流和字节流对文件的操作，包括创建文件路径，文件的读取和写入，文件判断，文件删除，遍历文件，文件复制，文件的编码与解码，文件异常处理以及对象序列化和反序列化等。
目录
24-复制文件的异常处理(try---catch代替throws)
26-序列化中的serialVersionUID和transient
1-File类的三个构造方法
import java.io.File;
public class FileDemo01
public static void main(String[] args)
//File封装路径
//创建File实例的三种方法
File file = new File("src\\\\com\\\\learn\\\\java.txt") ;
System.out.println(file);
File file1 = new File("src\\\\com\\\\learn","java.txt") ;
System.out.println(file1);
File file2 = new File("src\\\\com\\\\learn") ;
File file3 = new File(file2,"java.txt") ;
System.out.println(file3);
2-File类的创建功能
import java.io.File;
import java.io.IOException;
public class FileDemo02
public static void main(String[] args) throws IOException
//在目录下创建java.txt文件
File file = new File("New\\\\src\\\\com\\\\learn\\\\java.txt") ;
System.out.println(file.createNewFile());
System.out.println("------------------");
//在目录下创建目录study
File file1 = new File("New\\\\src\\\\com\\\\learn\\\\study") ;
System.out.println(file1.mkdir());
System.out.println("------------------");
//在目录下创建多级目录study1\\Java
File file2 = new File("New\\\\src\\\\com\\\\learn\\\\study1\\\\Java");
System.out.println(file2.mkdirs());
System.out.println("------------------");
3-File类判断和获取功能
import java.io.File;
import java.io.IOException;
public class FileDemo03
public static void main(String[] args) throws IOException
File file = new File("New\\\\src\\\\com\\\\learn\\\\java.txt");
file.createNewFile() ;
System.out.println(file.isFile()); //是否是文件
System.out.println(file.isDirectory()); //是否是目录
System.out.println(file.exists()); //是否存在
System.out.println(file.getAbsolutePath()); //绝对路径
System.out.println(file.getPath()); //抽象的路径
System.out.println(file.getName()); //最后的文件或者目录名
//返回文件和目录或者目录的字符串
File file1 = new File("New\\\\src") ;
String [] files = file1.list() ;
for(String s : files)
System.out.println(s);
//返回文件和目录的File对象
File [] files1 = file1.listFiles() ;
for(File file2 : files1)
System.out.println(file2);
4-File类删除功能
import java.io.File;
import java.io.IOException;
public class FileDemo04
public static void main(String[] args) throws IOException
//创建java.txt文件并删除
File file = new File("New\\\\src\\\\com\\\\learn\\\\java.txt") ;
file.createNewFile() ;
file.delete() ;
// System.out.println("------------");
//创建study目录并删除
File file1 = new File("New\\\\src\\\\com\\\\learn\\\\study") ;
file1.mkdir() ;
file1.delete() ;
// System.out.println("-------------");
//先创建目录,再创建文件,然后先删除文件,后删除目录
File file2 = new File("New\\\\src\\\\com\\\\learn\\\\study") ;
file2.mkdir() ;
File file3 = new File("New\\\\src\\\\com\\\\learn\\\\study","java.txt") ;
file3.createNewFile() ;
file3.delete() ;
file2.delete() ;
5-简单递归
import java.util.Scanner;
public class FileDemo05
public static void main(String[] args)
//递归求阶乘
Scanner input = new Scanner(System.in) ;
long n = input.nextLong() ;
System.out.println(f(n));
public static long f(long n)
return n==1 ? 1 : n * f(n-1) ;
6-遍历目录打印绝对路径
import java.io.File;
public class FileDemo06
public static void main(String[] args)
//遍历文件，输出绝对路径
File file = new File("New\\\\src") ;
findPath(file) ;
private static void findPath(File file)
if(file != null)
for (File file1 : file.listFiles())
if (file1.isDirectory())
findPath(file1); //是目录，递归调用
else
//不是目录,打印绝对路径
System.out.println(file1.getAbsolutePath());
7-字节流写数据的三种方式
import java.io.FileOutputStream;
import java.io.IOException;
public class FileDemo07
public static void main(String[] args) throws IOException
//true表示追加,如果没有true就默认为覆盖
FileOutputStream fos = new FileOutputStream("New\\\\src\\\\com\\\\learn\\\\java.txt",true) ;
fos.write(97); //写单个
fos.write("\\r\\n".getBytes());
fos.write("abcde\\r\\n".getBytes()); //写一组
fos.write("xyzw\\r\\n".getBytes(),1,3); //写指定长度
fos.close();
8-字节流读数据的方式
import java.io.FileInputStream;
import java.io.IOException;
public class FileDemo08
public static void main(String[] args) throws IOException
FileInputStream fis = new FileInputStream("New\\\\src\\\\com\\\\learn\\\\java.txt") ;
//读取一次数据
int by = fis.read() ;
System.out.println(by);
System.out.println((char)by);
//读取所有数据
while((by=fis.read()) != -1)
System.out.print((char)by);
fis.close();
9-字节流复制文本文件
import java.io.FileInputStream;
import java.io.FileOutputStream;
import java.io.IOException;
public class FileDemo09
public static void main(String[] args) throws IOException
//字节流依次读取文件内容并写入新文件
FileInputStream fis = new FileInputStream("New\\\\src\\\\com\\\\learn\\\\java.txt") ;
FileOutputStream fos = new FileOutputStream("New\\\\src\\\\com\\\\learn\\\\python.txt") ;
int by ;
while((by=fis.read()) != -1)
fos.write((char)by);
fis.close();
fos.close();
10-字节流读数据(一次读一组)
import java.io.FileInputStream;
import java.io.IOException;
public class FileDemo10
public static void main(String[] args) throws IOException
FileInputStream fis = new FileInputStream("New\\\\src\\\\com\\\\learn\\\\java.txt") ;
byte [] bytes = new byte[1024] ;
int len ;
while((len=fis.read(bytes)) != -1)
System.out.println(new String(bytes,0,len));
fis.close();
11-字节流复制图片
import java.io.FileInputStream;
import java.io.FileOutputStream;
import java.io.IOException;
public class FileDemo11
public static void main(String[] args) throws IOException
//字节流复制图片
FileInputStream fis = new FileInputStream("New\\\\src\\\\com\\\\learn\\\\x.jpg") ;
FileOutputStream fos = new FileOutputStream("New\\\\src\\\\com\\\\my\\\\x.jpg") ;
byte [] bytes = new byte[1024] ;
int len ;
while((len=fis.read(bytes)) != -1)
fos.write(bytes,0,len);
fis.close();
fos.close();
12-字节缓冲流读取数据
import java.io.BufferedInputStream;
import java.io.FileInputStream;
import java.io.IOException;
public class FileDemo12
public static void main(String[] args) throws IOException
//字节缓冲流
BufferedInputStream bis = new BufferedInputStream(new FileInputStream("New\\\\src\\\\com\\\\learn\\\\java.txt")) ;
byte [] bytes = new byte[1024] ;
int len ;
while((len=bis.read(bytes)) != -1)
System.out.println(new String(bytes,0,len));
13-初识编码与解码
import java.io.UnsupportedEncodingException;
import java.util.Arrays;
public class FileDemo13
public static void main(String[] args) throws UnsupportedEncodingException
String s = "中国" ;
//编码
byte [] bytes = s.getBytes("GBK") ;
byte [] bytes1 = s.getBytes("UTF-8") ;
System.out.println(Arrays.toString(bytes));
System.out.println(Arrays.toString(bytes1));
//解码
String s1 = new String(bytes,"GBK") ;
String s2 = new String(bytes1, "UTF-8") ;
System.out.println(s1);
System.out.println(s2);
14-字符流的编码与解码
import java.io.*;
public class FileDemo14
public static void main(String[] args) throws IOException
//以GBK编码字符流写入
OutputStreamWriter osw = new OutputStreamWriter(new FileOutputStream("New\\\\src\\\\com\\\\learn\\\\java.txt"),"GBK") ;
osw.write("中国");
osw.close();
//以GBK编码字符流读取
InputStreamReader osr = new InputStreamReader(new FileInputStream("New\\\\src\\\\com\\\\learn\\\\java.txt"),"GBK") ;
int len ;
while((len=osr.read()) != -1)
System.out.print((char) len);
15-字符流写数据的5种方式
import java.io.FileOutputStream;
import java.io.IOException;
import java.io.OutputStreamWriter;
public class FileDemo15
public static void main(String[] args) throws IOException
//字符流写数据的5种方式
OutputStreamWriter osw = new OutputStreamWriter(new FileOutputStream("New\\\\src\\\\com\\\\learn\\\\java.txt")) ;
//写单个字符
// osw.write("a");
// osw.flush();
// osw.close();
//写字符数组
// char [] chars = 'a','b','c','e','d' ;
// osw.write(chars);
// osw.flush();
// osw.close();
//写字符数组的一部分
// char [] chars1 = 'a','c','d','b' ;
// osw.write(chars1,1,2);
// osw.flush();
// osw.close();
//写字符串
// osw.write("abcdefg");
// osw.flush();
// osw.close();
//写字符串的一部分
osw.write("abcdefg",1,4);
osw.flush();
osw.close();
16-字符流读数据的2种方式
import java.io.FileInputStream;
import java.io.IOException;
import java.io.InputStreamReader;
public class FileDemo16
public static void main(String[] args) throws IOException
InputStreamReader isr = new InputStreamReader(new FileInputStream("New\\\\src\\\\com\\\\learn\\\\java.txt")) ;
//一次读取一个字符
int len ;
while((len=isr.read()) != -1)
System.out.print((char)len);
//一次读取一组字符
char [] bytes = new char[1024] ;
int by ;
while((by=isr.read(bytes)) != -1)
System.out.println(new String(bytes,0,by));
isr.close();
17-字符流复制文件
import java.io.*;
public class FileDemo17
public static void main(String[] args) throws IOException
InputStreamReader isr = new InputStreamReader(new FileInputStream("New\\\\src\\\\com\\\\learn\\\\java.txt")) ;
OutputStreamWriter osw = new OutputStreamWriter(new FileOutputStream("New\\\\src\\\\com\\\\my\\\\copy.txt")) ;
//
// //方法1：单个字符依次读写
// int len ;
// while ((len=isr.read()) != -1)
// osw.write(len);
//
// osw.close();
//方法2：一组字符的读写
int len ;
char [] chars = new char[1024] ;
while ((len = isr.read(chars)) != -1)
osw.write(chars,0,len);
osw.close();
isr.close();
import java.io.FileReader;
import java.io.FileWriter;
import java.io.IOException;
public class FileDemo18
public static void main(String[] args) throws IOException
FileReader fr = new FileReader("New\\\\src\\\\com\\\\learn\\\\java.txt") ;
FileWriter fw = new FileWriter("New\\\\src\\\\com\\\\my\\\\copy.txt") ;
//一次读写一个字符
// int len ;
// while((len=fr.read()) !=-1)
// fw.write(len);
//
// fw.close();
//一次写一组数据
int len ;
char [] chars = new char[1024] ;
while((len=fr.read(chars)) != -1)
fw.write(chars,0,len);
fr.close();
fw.close();
18-字符缓冲流复制文件
import java.io.*;
public class FileDemo19
public static void main(String[] args) throws IOException
BufferedReader br = new BufferedReader(new FileReader("New\\\\src\\\\com\\\\learn\\\\java.txt")) ;
BufferedWriter bw = new BufferedWriter(new FileWriter("New\\\\src\\\\com\\\\my\\\\copy.txt")) ;
//一次读写一个字符
// int len ;
while((len=br.read()) != -1)
bw.write(len);
br.close();
bw.close();
//一次写一组字符
int len ;
char [] chars = new char[1024] ;
while((len=br.read(chars)) != -1)
bw.write(chars,0,len);
bw.close();
br.close();
19-使用字符缓冲流特有功能复制文件
import java.io.*;
public class FileDemo20
public static void main(String[] args) throws IOException
BufferedReader br = new BufferedReader(new FileReader("New\\\\src\\\\com\\\\learn\\\\java.txt")) ;
BufferedWriter bw = new BufferedWriter(new FileWriter("New\\\\src\\\\com\\\\my\\\\copy.txt")) ;
String line ;
while ((line=br.readLine()) != null)
bw.write(line);
bw.newLine();
bw.flush();
bw.close();
br.close();
20-集合数据传入文件
import java.io.BufferedWriter;
import java.io.FileWriter;
import java.io.IOException;
import java.util.ArrayList;
public class FileDemo21
public static void main(String[] args) throws IOException
ArrayList<String> arrayList = new ArrayList<>() ;
arrayList.add("Java") ;
arrayList.add("python");
arrayList.add("c");
BufferedWriter bw = new BufferedWriter(new FileWriter("New\\\\src\\\\com\\\\learn\\\\java.txt"));
for(String s : arrayList)
bw.write(s);
bw.newLine();
bw.flush();
bw.close();
21-文件数据读入集合
import java.io.BufferedReader;
import java.io.FileReader;
import java.io.IOException;
import java.util.ArrayList;
public class FileDemo22
public static void main(String[] args) throws IOException
BufferedReader br = new BufferedReader(new FileReader("New\\\\src\\\\com\\\\learn\\\\java.txt")) ;
ArrayList<String> arrayList = new ArrayList<>() ;
String line ;
while((line = br.readLine()) != null)
arrayList.add(line);
for(String str : arrayList)
System.out.println(str);
22-复制单级文件夹(目录含文件，不含目录)
import java.io.*;
public class FileDemo23
/**
* 有2个问题需要注意
* 第一，该方法只能复制单级文件，即目录里不能含有目录，只能含有文件
* 第二，对于源路径和目标路径一定要具体到文件名，否则会拒绝访问
* @param args
* @throws IOException
*/
public static void main(String[] args) throws IOException
File srcFile = new File("D:\\\\files") ;
File destFile = new File("New\\\\src\\\\com\\\\my\\\\",srcFile.getName()) ;
if(!destFile.exists())
destFile.mkdir() ;
for(File files : srcFile.listFiles())
String name = files.getName() ;
File newFile = new File(destFile,name) ;
copyFiles(files,newFile) ;
private static void copyFiles(File srcFile, File newFile) throws IOException
BufferedInputStream bis = new BufferedInputStream(new FileInputStream(srcFile)) ;
BufferedOutputStream bos = new BufferedOutputStream(new FileOutputStream(newFile)) ;
byte [] bytes = new byte[1024] ;
int len ;
while((len=bis.read(bytes)) != -1)
bos.write(bytes,0,len);
bis.close();
bos.close();
23-复制多级文件夹(目录中包含目录和文件)
import java.io.*;
public class FileDemo24
public static void main(String[] args) throws IOException
File srcFile = new File("D:\\\\file") ;
File destFile = new File("New\\\\src\\\\com\\\\my") ;
copyFolder(srcFile,destFile) ;
private static void copyFolder(File srcFile, File destFile) throws IOException
//从源目录复制到目标目录
if(srcFile.isDirectory())
File newFile = new File(destFile,srcFile.getName()) ;
if(!newFile.exists())
newFile.mkdir() ;
for(File file : srcFile.listFiles())
copyFolder(file,newFile);
else //是文件，直接复制
File newFile = new File(destFile,srcFile.getName()) ;
copyFile1(srcFile,newFile);
private static void copyFile1(File srcFile, File newFile) throws IOException
BufferedInputStream bis = new BufferedInputStream(new FileInputStream(srcFile)) ;
BufferedOutputStream bos = new BufferedOutputStream(new FileOutputStream(newFile)) ;
int len ;
byte [] bytes = new byte[1024] ;
while((len=bis.read(bytes)) != -1)
bos.write(bytes,0,len);
bis.close();
bos.close();
24-复制文件的异常处理(try---catch代替throws)
import java.io.FileReader;
import java.io.FileWriter;
import java.io.IOException;
public class FileDemo25
public static void main(String[] args)
method1() ;
method2() ;
//方法1：直接进行try-catch处理异常
private static void method1()
FileReader fr = null;
FileWriter fw = null;
try
fr = new FileReader("New\\\\src\\\\com\\\\learn\\\\java.txt");
fw = new FileWriter("New\\\\src\\\\com\\\\my\\\\copy1.txt");
int len ;
char [] chars = new char[1024] ;
while((len=fr.read(chars)) != -1)
fw.write(chars,0,len);
catch (IOException e)
e.printStackTrace();
finally
try
if (fr != null)
fr.close();
catch (IOException e)
e.printStackTrace();
try
if (fw != null)
fw.close();
catch (IOException e)
e.printStackTrace();
//改进版本的异常处理
private static void method2()
try(
FileReader fr = new FileReader("New\\\\src\\\\com\\\\learn\\\\java.txt");
FileWriter fw = new FileWriter("New\\\\src\\\\com\\\\my\\\\copy2.txt");)
int len ;
char [] chars = new char[1024] ;
while((len=fr.read(chars)) != -1)
fw.write(chars,0,len);
catch (IOException e)
e.printStackTrace();
25-对象序列化流与对象反序列化流
import java.io.Serializable;
public class Student implements Serializable
private String name ;
private int age ;
public Student()
public Student(String name, int age)
this.name = name;
this.age = age;
public String getName()
return name;
public void setName(String name)
this.name = name;
public int getAge()
return age;
public void setAge(int age)
this.age = age;
import java.io.*;
public class FileDemo26
public static void main(String[] args) throws IOException, ClassNotFoundException
//对象序列化流
ObjectOutputStream oos = new ObjectOutputStream(new FileOutputStream("New\\\\src\\\\com\\\\my\\\\c.txt")) ;
Student student = new Student("张三", 18) ;
oos.writeObject(student);
oos.close();
//对象反序列化流
ObjectInputStream ois = new ObjectInputStream(new FileInputStream("New\\\\src\\\\com\\\\my\\\\c.txt")) ;
Object object = ois.readObject() ;
Student student1 = (Student) object ;
System.out.println(student1.getName() + "," + student1.getAge());
26-序列化中的serialVersionUID和transient
import java.io.Serializable;
public class Student implements Serializable
//加入序列化后修改类文件,会报错，需要加一个版本号
private static final long serialVersionUID = 42L ;
private transient String name ; //给变量加transient关键字,可以不被序列化
private int age ;
public Student()
public Student(String name, int age)
this.name = name;
this.age = age;
public String getName()
return name;
public void setName(String name)
this.name = name;
public int getAge()
return age;
public void setAge(int age)
this.age = age;
@Override
public String toString()
return "Student" +
"name='" + name + '\\'' +
", age=" + age +
'';
import java.io.*;
public class FileDemo26
public static void main(String[] args) throws IOException, ClassNotFoundException
//对象序列化流
ObjectOutputStream oos = new ObjectOutputStream(new FileOutputStream("New\\\\src\\\\com\\\\my\\\\c.txt")) ;
Student student = new Student("张三", 18) ;
oos.writeObject(student);
oos.close();
//对象反序列化流
ObjectInputStream ois = new ObjectInputStream(new FileInputStream("New\\\\src\\\\com\\\\my\\\\c.txt")) ;
Object object = ois.readObject() ;
Student student1 = (Student) object ;
System.out.println(student1.getName() + "," + student1.getAge());
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