java reads files and writes to files in a simple instance of of
- 2020-05-12 02:35:21
- OfStack
Java code
public class ReadFromFile {
/**
* Reads a file in bytes, often used for reading 2 Base files, such as pictures, sounds, images, etc.
*/
public static void readFileByBytes(String fileName) {
File file = new File(fileName);
InputStream in = null;
try {
System.out.println(" Read the contents of the file in bytes, 1 Time to read 1 Bytes: ");
// 1 Time to read 1 bytes
in = new FileInputStream(file);
int tempbyte;
while ((tempbyte = in.read()) != -1) {
System.out.write(tempbyte);
}
in.close();
} catch (IOException e) {
e.printStackTrace();
return;
}
try {
System.out.println(" Read the contents of the file in bytes, 1 Multiple bytes per read: ");
// 1 Multiple bytes per read
byte[] tempbytes = new byte[100];
int byteread = 0;
in = new FileInputStream(fileName);
ReadFromFile.showAvailableBytes(in);
// Reading multiple bytes into a byte array, byteread for 1 Number of bytes per read
while ((byteread = in.read(tempbytes)) != -1) {
System.out.write(tempbytes, 0, byteread);
}
} catch (Exception e1) {
e1.printStackTrace();
} finally {
if (in != null) {
try {
in.close();
} catch (IOException e1) {
}
}
}
}
/**
* To read a file in character units, often used to read text, Numbers, and other types of files
*/
public static void readFileByChars(String fileName) {
File file = new File(fileName);
Reader reader = null;
try {
System.out.println(" Read the contents of the file in characters, 1 Time to read 1 Bytes: ");
// 1 Time to read 1 A character
reader = new InputStreamReader(new FileInputStream(file));
int tempchar;
while ((tempchar = reader.read()) != -1) {
// for windows Next, \r\n These two characters are in 1 When rising, represents 1 A line feed.
// But if the two characters are displayed separately, the lines are changed twice.
// So, shield it \r Or shielding \n . Otherwise, there will be many more blank lines.
if (((char) tempchar) != '\r') {
System.out.print((char) tempchar);
}
}
reader.close();
} catch (Exception e) {
e.printStackTrace();
}
try {
System.out.println(" Read the contents of the file in characters, 1 Multiple bytes per read: ");
// 1 Read more than one character at a time
char[] tempchars = new char[30];
int charread = 0;
reader = new InputStreamReader(new FileInputStream(fileName));
// Read multiple characters into a character array, charread for 1 Number of times read characters
while ((charread = reader.read(tempchars)) != -1) {
// Again shielding \r Don't show
if ((charread == tempchars.length)
&& (tempchars[tempchars.length - 1] != '\r')) {
System.out.print(tempchars);
} else {
for (int i = 0; i < charread; i++) {
if (tempchars[i] == '\r') {
continue;
} else {
System.out.print(tempchars[i]);
}
}
}
}
} catch (Exception e1) {
e1.printStackTrace();
} finally {
if (reader != null) {
try {
reader.close();
} catch (IOException e1) {
}
}
}
}
/**
* Read a file as a behavior unit, often used to read a line-oriented formatted file
*/
public static void readFileByLines(String fileName) {
File file = new File(fileName);
BufferedReader reader = null;
try {
System.out.println(" Read the contents of the file as a behavior unit, 1 Time to read 1 The whole line: ");
reader = new BufferedReader(new FileReader(file));
String tempString = null;
int line = 1;
// 1 Time to read 1 Ok, until you read in null End for file
while ((tempString = reader.readLine()) != null) {
// According to the line Numbers
System.out.println("line " + line + ": " + tempString);
line++;
}
reader.close();
} catch (IOException e) {
e.printStackTrace();
} finally {
if (reader != null) {
try {
reader.close();
} catch (IOException e1) {
}
}
}
}
/**
* Read the contents of the file at random
*/
public static void readFileByRandomAccess(String fileName) {
RandomAccessFile randomFile = null;
try {
System.out.println(" Random reads 1 Section file content: ");
// Open the 1 Three random access file streams, in a read-only mode
randomFile = new RandomAccessFile(fileName, "r");
// File length, number of bytes
long fileLength = randomFile.length();
// The start of the read file
int beginIndex = (fileLength > 4) ? 4 : 0;
// Moves the start of the read file to beginIndex Position.
randomFile.seek(beginIndex);
byte[] bytes = new byte[10];
int byteread = 0;
// 1 Time to read 10 Bytes if the file is short of content 10 Bytes, read the remaining bytes.
// will 1 The number of bytes assigned for each read byteread
while ((byteread = randomFile.read(bytes)) != -1) {
System.out.write(bytes, 0, byteread);
}
} catch (IOException e) {
e.printStackTrace();
} finally {
if (randomFile != null) {
try {
randomFile.close();
} catch (IOException e1) {
}
}
}
}
/**
* Displays the number of bytes left in the input stream
*/
private static void showAvailableBytes(InputStream in) {
try {
System.out.println(" The number of bytes in the current byte input stream is :" + in.available());
} catch (IOException e) {
e.printStackTrace();
}
}
public static void main(String[] args) {
String fileName = "C:/temp/newTemp.txt";
ReadFromFile.readFileByBytes(fileName);
ReadFromFile.readFileByChars(fileName);
ReadFromFile.readFileByLines(fileName);
ReadFromFile.readFileByRandomAccess(fileName);
}
}
Java code
public class AppendToFile {
/**
* A Method append file: use RandomAccessFile
*/
public static void appendMethodA(String fileName, String content) {
try {
// Open the 1 Random access to the file stream, by read and write
RandomAccessFile randomFile = new RandomAccessFile(fileName, "rw");
// File length, number of bytes
long fileLength = randomFile.length();
// Moves the write file pointer to the end of the file.
randomFile.seek(fileLength);
randomFile.writeBytes(content);
randomFile.close();
} catch (IOException e) {
e.printStackTrace();
}
}
/**
* B Method append file: use FileWriter
*/
public static void appendMethodB(String fileName, String content) {
try {
// Open the 1 File writer, the first in the constructor 2 A parameter true Means to write a file as an append
FileWriter writer = new FileWriter(fileName, true);
writer.write(content);
writer.close();
} catch (IOException e) {
e.printStackTrace();
}
}
public static void main(String[] args) {
String fileName = "C:/temp/newTemp.txt";
String content = "new append!";
// According to the method A Additional documents
AppendToFile.appendMethodA(fileName, content);
AppendToFile.appendMethodA(fileName, "append end. \n");
// Display file contents
ReadFromFile.readFileByLines(fileName);
// According to the method B Additional documents
AppendToFile.appendMethodB(fileName, content);
AppendToFile.appendMethodB(fileName, "append end. \n");
// Display file contents
ReadFromFile.readFileByLines(fileName);
}
}