1, FileInputStream
| method | explain |
| int available() | Returns an estimate of the number of bytes that can be read (or skipped) from the input stream without blocking, which may be 0, or 0 when the end of the stream is detected |
| int read() | Write a character to the stream |
| int read(byte[] b) | Read multiple bytes into b array |
| int read(byte[] b, int off, int len) | Read multiple bytes from the stream and fill them in the specified position in the array |
| void reset() | Reset flow |
| log skip(long n) | Skip multiple characters |
| void close() | Close flow |
public class TestFile {
public static void main(String[] args) {
//Read temp Txt file content
//The stream must be closed after use!!! Write in finally
FileInputStream fis = null;
try {
fis = new FileInputStream("D:\\Lession\\Java2113\\temp.txt");
int temp = 0;
while((temp = fis.read())!=-1) {
System.out.println(temp);
}
} catch (FileNotFoundException e) {
e.printStackTrace();
} catch (IOException e) {
e.printStackTrace();
} finally {
try {
fis.close();
} catch (IOException e) {
e.printStackTrace();
}
}
}
}Read (byte [] b): read the content into byte [] and the result is the number of bytes read. If no bytes are read, return - 1
public static void main(String[] args) {
//Which file to read
FileInputStream fis = null;
/*File file = new File("D:\\Lession\\Java2113\\temp.txt");
try {
fis = new FileInputStream(file);
} catch (FileNotFoundException e) {
// TODO Auto-generated catch block
e.printStackTrace();
}*/
try {
fis = new FileInputStream("D:\\Lession\\Java2113\\temp.txt");
//Read a byte and return the unicode value of the byte
//fis.read();
//Read into byte [] and return the read length
//fis.read(byte[] b);
//Read into byte [] and specify the position of byte array
//fis.read(byte[] b, int off, int len)
/* System.out.println((char)fis.read());
System.out.println(fis.read());
System.out.println(fis.read());
System.out.println(fis.read());
System.out.println(fis.read()); //-1
*/ /*int temp = 0;
while((temp=fis.read())!=-1) {
System.out.println((char)temp);
}*/
//buffer
byte[] bytes = new byte[10];
int temp = 0;
while((temp=fis.read(bytes))!=-1) {
for(int i = 0;i<temp;i++) {
System.out.println((char)bytes[i]);
}
}
} catch (FileNotFoundException e) {
e.printStackTrace();
} catch (IOException e) {
e.printStackTrace();
} finally {
try {
fis.close();
} catch (IOException e) {
e.printStackTrace();
}
}
}Buffer: as in life, moving books from one classroom to another will be slow and tiring if you move them one by one, such as the use of int read() method;
If a schoolbag is used as a carrying tool, it will be faster to carry the books in the classroom into the schoolbag. There is a buffering process of loading books into the schoolbag, for example, the use of int read (byte [] b) method
Read Chinese
public static void main(String[] args) {
FileInputStream fis = null;
try {
fis = new FileInputStream("D:\\Lession\\Java2113\\temp.txt");
byte[] bytes = new byte[fis.available()];
int temp = 0;
if((temp=fis.read(bytes))!=-1) {
System.out.println(new String(bytes,"UTF-8"));
}
} catch (FileNotFoundException e) {
e.printStackTrace();
} catch (IOException e) {
e.printStackTrace();
} finally {
try {
fis.close();
} catch (IOException e) {
e.printStackTrace();
}
}
}2, FileOutputStream
| method | explain |
| void write(byte b) | Write a byte to the stream |
| void write(byte[] str) | Write a byte array to the stream |
| void write(byte[] b, int off, int len) | Writes a portion of a byte array to a stream |
| void flush() | Refresh stream |
| void close() | Close flow |
Constructor:
FileOutputStream(File file) adds new content from the beginning by default, overwriting.
Fileoutputstream (file, Boolean append) appends content from the end
public class TestFileOutputStream {
public static void main(String[] args) {
//To temp Write abcd in TXT
FileOutputStream fos = null;
try {
fos = new FileOutputStream("D:\\Lession\\Java2113\\temp.txt");
fos.write("Abel measured".getBytes());
} catch (FileNotFoundException e) {
e.printStackTrace();
} catch (IOException e) {
e.printStackTrace();
}
}
}Apply: copy one file to another
public static void copy1(String srcPath,String destPath) {
FileInputStream fis = null;
FileOutputStream fos = null;
byte[] bytes = new byte[1024];
try {
fis = new FileInputStream(srcPath);
fos = new FileOutputStream(destPath);
int temp = 0;
while ((temp = fis.read(bytes)) != -1) {
fos.write(bytes, 0, temp);
}
} catch (FileNotFoundException e) {
e.printStackTrace();
} catch (IOException e) {
e.printStackTrace();
} finally {
try {
fis.close();
} catch (IOException e) {
e.printStackTrace();
}
try {
fos.close();
} catch (IOException e) {
e.printStackTrace();
}
}
}3, BufferedInputStream/BufferedOutputStream
public static void copy2(String srcPath,String destPath) {
FileInputStream fis = null;
FileOutputStream fos = null;
BufferedInputStream bis = null;
BufferedOutputStream bos = null;
try {
fis = new FileInputStream(srcPath);
fos = new FileOutputStream(destPath);
bis = new BufferedInputStream(fis);
bos = new BufferedOutputStream(fos,1024);
int temp = 0;
while((temp=bis.read())!=-1) {
//By default, the buffer stream is output to the device when the buffer is full
bos.write(temp);
}
//Manual flushing buffer output to equipment
bos.flush();//Scour and read the last part less than 1024
} catch (FileNotFoundException e) {
e.printStackTrace();
} catch (IOException e) {
e.printStackTrace();
}finally {
try {
bis.close();
} catch (IOException e1) {
e1.printStackTrace();
}
try {
bos.close();
} catch (IOException e1) {
e1.printStackTrace();
}
try {
fis.close();
} catch (IOException e) {
e.printStackTrace();
}
try {
fos.close();
} catch (IOException e) {
e.printStackTrace();
}
}
}Finally, you need to flush!!!
4, FileReader and FileWriter
Subclasses of Reader and Writer are character streams
public class TestFileReader {
public static void main(String[] args) {
FileReader fr = null;
try {
fr = new FileReader("D:\\Lession\\Java2113\\temp1.txt");
int temp = 0;
char[] chars = new char[2];
while((temp=fr.read(chars))!=-1) {
for(char c:chars) {
System.out.println(c);
}
}
} catch (FileNotFoundException e) {
e.printStackTrace();
} catch (IOException e) {
e.printStackTrace();
}
}
}public class TestFileWriter {
public static void main(String[] args) {
try {
FileWriter fw = new FileWriter("D:\\Lession\\Java2113\\temp1.txt");
fw.write("Hello China");
fw.flush();
} catch (IOException e) {
e.printStackTrace();
}
}
}
5, BufferedReader and BufferedWriter
BufferedReader provides the function of reading by line
BufferedWriter provides the ability to customize the buffer size
FileReader fr = null;
try {
fr = new FileReader("D:\\Lession\\Java2113\\temp1.txt");
BufferedReader br = new BufferedReader(fr);
String str = null;
while((str=br.readLine())!=null) {
System.out.println(str);
}
} catch (FileNotFoundException e) {
e.printStackTrace();
} catch (IOException e) {
e.printStackTrace();
}
try {
FileWriter fw = new FileWriter("D:\\Lession\\Java2113\\temp1.txt");
BufferedWriter br = new BufferedWriter(fw,1024);
br.write("Hello, Beijing");
br.flush();
} catch (IOException e) {
e.printStackTrace();
}6, InputStreamReader and OutputStreamWriter (transform stream)
Both character streams are inherited from Reader and Writer, which is a bridge for bytes to flow into character stream
public static void main(String[] args) {
try {
FileInputStream fis = new FileInputStream("D:\\Lession\\Java2113\\temp.txt");
InputStreamReader reader = new InputStreamReader(fis,"UTF-8");
int temp = 0;
while((temp=reader.read())!=-1) {
System.out.println((char)temp);
}
} catch (FileNotFoundException e) {
e.printStackTrace();
} catch (IOException e) {
e.printStackTrace();
}
}public static void main(String[] args) {
try {
FileOutputStream fos = new FileOutputStream("D:\\Lession\\Java2113\\temp1.txt");
/*fos.write("Hello, Beijing ". getBytes());*/
OutputStreamWriter osw = new OutputStreamWriter(fos);
osw.write("Hello, Beijing");
osw.flush();
} catch (FileNotFoundException e) {
e.printStackTrace();
} catch (IOException e) {
e.printStackTrace();
}
}7, PrintWriter
public static void main(String[] args) {
PrintWriter pw = null;
try {
FileOutputStream fos = new FileOutputStream("D:\\Lession\\Java2113\\temp1.txt");
pw = new PrintWriter(fos,true);
pw.println("Hello, Beijing");
pw.println("Hello, Winter Olympics");
} catch (FileNotFoundException e) {
e.printStackTrace();
}
}8, DataInputStream and DataOutputStream
Byte stream for reading and writing data (basic type data)
try {
FileOutputStream fos = new FileOutputStream("D:\\Lession\\Java2113\\temp1.txt");
DataOutputStream dos = new DataOutputStream(fos);
dos.writeInt(1);
} catch (IOException e) {
// TODO Auto-generated catch block
e.printStackTrace();
}
public static void main(String[] args) {
try {
FileInputStream fis = new FileInputStream("D:\\Lession\\Java2113\\temp1.txt");
DataInputStream dis = new DataInputStream(fis);
System.out.println(dis.readInt());
} catch (IOException e) {
e.printStackTrace();
}
}