文章目录
FileIO_字节流IO_字符流文件上传下载
File
常用构造
File(String pathname
) 目录路径
/文件路径
File(String parent
, String child
) == File(File parent
, String child
)
parent： 父级目录 child
: 子级文件名称
操作文件
1. boolean exists() 判断文件
/目录是否存在
2. String
getName() 获得文件或者目录名称
3. boolean createNewFile() 创建文件
4. long length() 获得文件内容大小
5. boolean delete() 删除文件
6. boolean isFile() 判断是否是文件
操作目录
1. boolean mkdir()
2. boolean mkdirs()
3. String
[] list() 获得当前目录下的子目录和子文件名称
4. File
[] listFiles() 获得当前目录下的子目录和子文件
递归（遍历当前路径下的所有文件）
private static void demo4(File file
,String string
) {
Objects
.requireNonNull(file
);
if(!file
.exists()){
System
.out
.println("当前路径不存在");
return;
}
String
[] fileNames
= file
.list();
for (String str
:fileNames
){
File child
= new File(file
, str
);
if(child
.isDirectory()){
System
.out
.println(string
+str
);
demo4(child
,"| "+string
);
}else{
System
.out
.println(string
+str
);
}
}
}
private static void demo5(File file
, String s
) {
File
[] files
= file
.listFiles();
for (File fi
:files
){
if(fi
.isDirectory()){
System
.out
.println(s
+fi
.getName());
demo5(fi
,"| "+s
);
}else{
System
.out
.println(s
+fi
.getName());
}
}
}
文件过滤
File
[] listFiles(FileFilter filter
)
File
[] listFiles(FilenameFilter filter
)
private static void demo7(File file
, String s
) {
File
[] files
= file
.listFiles((parent
, name
)->{
if(new File(parent
,name
).isDirectory()){
return true;
}
return name
.endsWith("java");
});
}
File
[] files
= file
.listFiles(child
->{
if(child
.isDirectory()){
return true;
}
return child
.getName().endsWith("java");
});
IO_字节流
读入写出在计算机里面，所有的文件都是二进制的文件， 操作文件内容都是通过字节。图片 文本 音频 压缩 都是以字节进行存储的， 字节流可以操作计算机里面任意类型的文件。字节输入流——InputStream
常用子类：FileInputStream BufferedInputStream DataInputStream ObjectInputStream
public abstract class InputStream extends Object implements Closeable
int available() 获得当前输入流对象有效的字节数
===> file
.length()
void close() 关闭流
abstract int read() 一次一个字节进行读取 读到末尾
-1
int read(byte[] b
) 一次读取b
.length个字节 存储到
byte[] 返回值读到的有效字节个数
-1
int read(byte[] b
, int off
, int len
) off：从指定
byte[]索引位置写入
一次读取len个字节 存到
byte[] 数组中 返回值读到的有效字节个数
-1
效率高低；
读取文件大小内容一定的：
100个字节
read() 读取
100次 打印
100次
read(byte[50]) 读了
100次 打印
2次 适合大文件的读取
FileInputStream(File file
)
FileInputStream(String name
)
private static void demo2(String path
) {
try (
InputStream inputStream
= new FileInputStream(path
);
) {
byte[] bytes
= new byte[1024];
int content
= 0;
while ((content
= inputStream
.read(bytes
)) != -1) {
System
.out
.println(new String(bytes
, 0, content
));
}
} catch (FileNotFoundException e
) {
e
.printStackTrace();
} catch (IOException e
) {
e
.printStackTrace();
}
}
字节输出流——OutputStream（若目标文件不存在，输出流会自动创建目标文件）
public abstract class OutputStream extends Object implements Closeable, Flushable
void close()
void write(byte[] b
) 一次写b
.length个字节
void write(byte[] b
, int off
, int len
)
void write(int b
) 一次写一个字节内容
FileOutputStream(String name
)
FileOutputStream(String name
, boolean append
) append
: 是否会在末尾追加文本数据 默认：
false
public class OutPutStreamDemo {
public static void main(String
[] args
) {
demo1();
}
private static void demo1() {
try (
OutputStream outputStream
= new FileOutputStream("a.txt",false)
) {
byte[] bytes
= "我们在学习".getBytes();
outputStream
.write(bytes
,0,bytes
.length
);
System
.out
.println("写入完毕。。。。。。。");
} catch (FileNotFoundException e
) {
e
.printStackTrace();
} catch (IOException e
) {
e
.printStackTrace();
}
}
}
高效字节流
高效字节流： 自带一个缓冲区
byte[] buf
= 8192
BufferedInputStream
BufferedOutPutStream
BufferedInputStream(InputStream in
)
BufferedOutputStream(OutputStream out
)
IO_字符流
字符流 = 字节流+编码 (GBK UTF-8) ，只能针对于文本文件(txt、 java)字符输入流——Reader
常用子类: FileReder BufferedReader InputStreamReader
public class ReaderDemo {
public static void main(String
[] args
) {
demo3();
}
private static void demo3() {
try(
Reader reader
= new FileReader("D:\\idea_workspace\\one\\day15\\src\\com\\javasm\\io\\InputStreamDemo.java");
){
char[] chars
= new char[1024];
int len
= 0;
while ((len
=reader
.read(chars
,0,chars
.length
))!=-1){
System
.out
.println(new String(chars
,0,len
));
}
} catch (FileNotFoundException e
) {
e
.printStackTrace();
} catch (IOException e
) {
e
.printStackTrace();
}
}
private static void demo2() {
try(
Reader reader
= new FileReader("D:\\idea_workspace\\one\\day15\\src\\com\\javasm\\io\\InputStreamDemo.java");
){
char[] chars
= new char[1024];
int len
= 0;
while ((len
=reader
.read(chars
))!=-1){
System
.out
.println(new String(chars
));
}
} catch (FileNotFoundException e
) {
e
.printStackTrace();
} catch (IOException e
) {
e
.printStackTrace();
}
}
private static void demo1() {
try(
Reader reader
= new FileReader("D:\\idea_workspace\\one\\day15\\src\\com\\javasm\\io\\InputStreamDemo.java");
){
int len
= 0;
while ((len
=reader
.read())!=-1){
System
.out
.print((char)len
);
}
} catch (FileNotFoundException e
) {
e
.printStackTrace();
} catch (IOException e
) {
e
.printStackTrace();
}
}
}
字符输出流——Writer
public abstract class Writer
extends Object
implements Appendable, Closeable
, Flushable
void write(char[] cbuf
)
void write(char[] cbuf
, int off
, int len
)
void write(String str
)
void write(int c
)
Writer
append(CharSequence csq
)
FileWriter(String fileName
)
FileWriter(String fileName
, boolean append
) false
public class WriterDemo {
public static void main(String
[] args
) {
try(
Writer writer
= new FileWriter("b.txt",true)
){
writer
.write('a');
writer
.write('\n');
writer
.write("我们".toCharArray());
writer
.write("在学习java");
writer
.append("水果为单位dhdgs");
} catch (IOException e
) {
e
.printStackTrace();
}
}
}
文件上传下载
public class FileUtil {
private FileUtil() {
}
public static void copyFile4(String sourceFile
, String targetFile
) {
try (
BufferedReader bufferedReader
= new BufferedReader(new FileReader(sourceFile
));
BufferedWriter bufferedWriter
= new BufferedWriter(new FileWriter(targetFile
));
) {
String content
= "";
while ((content
= bufferedReader
.readLine()) != null
) {
bufferedWriter
.write(content
);
bufferedWriter
.newLine();
}
System
.out
.println("success");
} catch (FileNotFoundException e
) {
e
.printStackTrace();
} catch (IOException e
) {
e
.printStackTrace();
}
}
public static void copyFile3(String sourceFile
, String targetFile
) {
try (
Reader reader
= new FileReader(sourceFile
);
Writer writer
= new FileWriter(targetFile
);
) {
char[] chars
= new char[1024];
int len
= 0;
while ((len
= reader
.read(chars
)) != -1) {
writer
.write(chars
, 0, len
);
}
System
.out
.println("success");
} catch (FileNotFoundException e
) {
e
.printStackTrace();
} catch (IOException e
) {
e
.printStackTrace();
}
}
public static void copyFile2(String sourceFile
, String targetFile
) {
try (
BufferedInputStream bufferedInputStream
= new BufferedInputStream(new URL(sourceFile
).openStream());
BufferedOutputStream outputStream
= new BufferedOutputStream(new FileOutputStream(targetFile
));
) {
int len
= 0;
byte[] by
= new byte[1024];
while ((len
= bufferedInputStream
.read(by
)) != -1) {
outputStream
.write(by
, 0, len
);
}
} catch (FileNotFoundException e
) {
e
.printStackTrace();
} catch (IOException e
) {
e
.printStackTrace();
}
}
public static void copyFile1(String sourceFile
, String targetFile
) {
try (
InputStream inputStream
= new FileInputStream(sourceFile
);
OutputStream outputStream
= new FileOutputStream(targetFile
);
) {
byte[] bytes
= new byte[1024 * 10];
int len
= 0;
while ((len
= inputStream
.read(bytes
)) != -1) {
outputStream
.write(bytes
, 0, len
);
}
System
.out
.println("文件复制成功。。。。。");
} catch (FileNotFoundException e
) {
e
.printStackTrace();
} catch (IOException e
) {
e
.printStackTrace();
}
}
public static void copyFile(String sourceFile
, String targetFile
) {
try (
InputStream inputStream
= new FileInputStream(sourceFile
);
OutputStream outputStream
= new FileOutputStream(targetFile
);
) {
int len
= 0;
while ((len
= inputStream
.read()) != -1) {
outputStream
.write(len
);
}
System
.out
.println("文件复制成功。。。。。");
} catch (FileNotFoundException e
) {
e
.printStackTrace();
} catch (IOException e
) {
e
.printStackTrace();
}
}
}
