目录
输入输出流
输出流
输入流
File类
文件可以认为是相关记录或放在一起的数据集合
在java中，使用java.io.File类对文件进行操作
绝对路径和相对路径
绝对路径：从盘符开始的路径
相对路径：是从当前路径开始的路径
package com.imooc.file;
import java.io.File;
import java.io.IOException;
public class FileDemo {
public static void main(String[] args) {
//创建File对象
// File file1=new File("F:\\javaWork\\imooc\\IOProj\\score.txt");
// File file1=new File("F:\\javaWork","imooc\\IOProj\\score.txt");
File file=new File("F:\\javaWork");
File file1=new File(file,"imooc\\IOProj\\imooc.txt");
//判断文件是否存在
System.out.println("是否是目录："+file1.isDirectory());
System.out.println("是否是文件："+file1.isFile());
//创建目录 多级目录用mkdirs()
File file2=new File("F:\\javaWork\\imooc\\IOProj\\HashSet");
if(!file2.exists()) {
file2.mkdir();
}
//创建文件
if(!file1.exists()) {
try {
file1.createNewFile();
} catch (IOException e) {
// TODO Auto-generated catch block
e.printStackTrace();
}
}
}
}
字节流
字节输入流：InputStream
字节输出流：OutputStream
FileInputStream
- 从文件系统中的某个文件中获得输入字节
- 用于读取诸如图像数据之类的原生字节流
package com.imooc.file;
import java.io.FileInputStream;
import java.io.FileNotFoundException;
import java.io.IOException;
public class FileInputDemo2 {
public static void main(String[] args) {
// 创建一个FileInputStream对象
try {
FileInputStream fis = new FileInputStream("imooc.txt");
byte[] b=new byte[100];
fis.read(b,0,5);
System.out.println(new String(b));
fis.close();
} catch (FileNotFoundException e) {
e.printStackTrace();
} catch (IOException e) {
e.printStackTrace();
}
}
}
FileOutputStream
package com.imooc.file;
import java.io.FileInputStream;
import java.io.FileNotFoundException;
import java.io.FileOutputStream;
import java.io.IOException;
public class FileOutputDemo {
public static void main(String[] args) {
FileOutputStream fos;
FileInputStream fis;
try {
fos = new FileOutputStream("imooc.txt",true);
fis=new FileInputStream("imooc.txt");
fos.write(50);
fos.write('a');
System.out.println(fis.read());
System.out.println((char)fis.read());
fos.close();
fis.close();
} catch (FileNotFoundException e) {
// TODO Auto-generated catch block
e.printStackTrace();
} catch (IOException e) {
e.printStackTrace();
}
}
}
package com.imooc.file;
import java.io.FileInputStream;
import java.io.FileNotFoundException;
import java.io.FileOutputStream;
import java.io.IOException;
public class FileOutputDemo1 {
public static void main(String[] args) {
// 文件拷贝
try {
FileInputStream fis=new FileInputStream("happy.gif");
FileOutputStream fos=new FileOutputStream("happycopy.gif");
int n=0;
byte[] b=new byte[1024];
while((n=fis.read(b))!=-1){
fos.write(b,0,n);
}
fis.close();
fos.close();
} catch (FileNotFoundException e) {
// TODO Auto-generated catch block
e.printStackTrace();
}catch(IOException e){
e.printStackTrace();
}
}
}
缓冲流
缓冲输入流：BufferedInputStream
缓冲输出流：BufferedOutputStream
package com.imooc.file;
import java.io.BufferedInputStream;
import java.io.BufferedOutputStream;
import java.io.FileInputStream;
import java.io.FileNotFoundException;
import java.io.FileOutputStream;
import java.io.IOException;
public class BufferedDemo {
public static void main(String[] args) {
try {
FileOutputStream fos=new FileOutputStream("imooc.txt");
BufferedOutputStream bos=new BufferedOutputStream(fos);
FileInputStream fis=new FileInputStream("imooc.txt");
BufferedInputStream bis=new BufferedInputStream(fis);
long startTime=System.currentTimeMillis();
bos.write(50);
bos.write('a');
bos.flush();
System.out.println(bis.read());
System.out.println((char)bis.read());
long endTime=System.currentTimeMillis();
System.out.println(endTime-startTime);
fos.close();
bos.close();
fis.close();
bis.close();
} catch (FileNotFoundException e) {
// TODO Auto-generated catch block
e.printStackTrace();
}catch (IOException e) {
// TODO Auto-generated catch block
e.printStackTrace();
}
}
}
字符流
字符输入流：Reader
字符输出流：Writer
字节字符转换流
- InputStreamReader
- OutputStreamWriter
package com.imooc.charstream;
import java.io.BufferedReader;
import java.io.BufferedWriter;
import java.io.FileInputStream;
import java.io.FileNotFoundException;
import java.io.FileOutputStream;
import java.io.IOException;
import java.io.InputStreamReader;
import java.io.OutputStreamWriter;
public class ReaderDemo {
// 把imooc.txt复制到imooc1.txt中
public static void main(String[] args) {
try {
FileInputStream fis = new FileInputStream("imooc.txt");
InputStreamReader isr = new InputStreamReader(fis, "GBK");
BufferedReader br = new BufferedReader(isr);
FileOutputStream fos = new FileOutputStream("imooc1.txt");
OutputStreamWriter osw = new OutputStreamWriter(fos, "GBK");
BufferedWriter bw = new BufferedWriter(osw);
int n = 0;
char[] cbuf = new char[10];
// while((n=isr.read())!=-1){
// System.out.print((char)n);
// }
// while((n=isr.read(cbuf))!=-1){
// String s=new String(cbuf,0,n);
// System.out.print(s);
// }
while ((n = br.read(cbuf)) != -1) {
// String s=new String(cbuf,0,n);
bw.write(cbuf, 0, n);
bw.flush();
}
fis.close();
fos.close();
isr.close();
osw.close();
br.close();
bw.close();
} catch (FileNotFoundException e) {
// TODO Auto-generated catch block
e.printStackTrace();
} catch (IOException e) {
// TODO Auto-generated catch block
e.printStackTrace();
}
}
}
对象序列化
步骤：
- 创建一个类，继承Serializable接口
- 创建对象
- 将对象写入文件
- 从文件读取对象信息
- 对象输入流 ObjectInputStream
- 对象输出流 ObjectOutputStream
package com.imooc.serial;
import java.io.FileInputStream;
import java.io.FileNotFoundException;
import java.io.FileOutputStream;
import java.io.IOException;
import java.io.ObjectInputStream;
import java.io.ObjectOutputStream;
public class GoodsTest {
public static void main(String[] args) {
// 定义Goods类的对象
Goods goods1 = new Goods("gd001", "电脑", 3000);
try {
FileOutputStream fos = new FileOutputStream("imooc.txt");
ObjectOutputStream oos = new ObjectOutputStream(fos);
FileInputStream fis = new FileInputStream("imooc.txt");
ObjectInputStream ois = new ObjectInputStream(fis);
// 将Goods对象信息写入文件
oos.writeObject(goods1);
oos.writeBoolean(true);
oos.flush();
// 读对象信息
try {
Goods goods = (Goods) ois.readObject();
System.out.println(goods);
} catch (ClassNotFoundException e) {
// TODO Auto-generated catch block
e.printStackTrace();
}
System.out.println(ois.readBoolean());
fos.close();
oos.close();
fis.close();
ois.close();
} catch (FileNotFoundException e) {
// TODO Auto-generated catch block
e.printStackTrace();
} catch (IOException e) {
// TODO Auto-generated catch block
e.printStackTrace();
}
}
}