import java.io.BufferedReader;

import java.io.File;

import java.io.FileInputStream;

import java.io.FileReader;

import java.io.IOException;

import java.io.InputStream;

import java.io.InputStreamReader;

import java.io.RandomAccessFile;

import java.io.Reader;

public class ReadFromFile {

/**

* Read file by byte, for sound and image files

* @param fileName targetfile name

*/

public static void readFileByBytes(String fileName){

File file = new File(fileName);

InputStream in = null;

try {

System.out.println("Read file by byte");

// One byte at each time

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 file by byte, multiple bytes one time");

//multiple bytes one time

byte[] tempbytes = new byte[100];

int byteread = 0;

in = new FileInputStream(fileName);

ReadFromFile.showAvailableBytes(in);

//byteread = length

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) {

}

}

}

}

/**

* Read file by char, use for text and number files

* @param fileName

*/

public static void readFileByChars(String fileName){

File file = new File(fileName);

Reader reader = null;

try {

System.out.println("Read file by char, one char each time");

reader = new InputStreamReader(new FileInputStream(file));

int tempchar;

while ((tempchar = reader.read()) != -1){

//because under windows, rn mean new line, when these two chars split, there will be two new lines.

//delete r can deduce useless blank lines

if (((char)tempchar) != 'r'){

System.out.print((char)tempchar);

}

}

reader.close();

} catch (Exception e) {

e.printStackTrace();

}

try {

System.out.println("Read file by chars, multiple chars each time");

char[] tempchars = new char[30];

int charread = 0;

reader = new InputStreamReader(new FileInputStream(fileName));

while ((charread = reader.read(tempchars))!=-1){

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 file by line

* @param fileName

*/

public static void readFileByLines(String fileName){

File file = new File(fileName);

BufferedReader reader = null;

try {

System.out.println("Read file by line: ");

reader = new BufferedReader(new FileReader(file));

String tempString = null;

int line = 1;

while ((tempString = reader.readLine()) != null){

//line number

System.out.println("line " + line + ": " + tempString);

line++;

}

reader.close();

} catch (IOException e) {

e.printStackTrace();

} finally {

if (reader != null){

try {

reader.close();

} catch (IOException e1) {

}

}

}

}

/**

* Random read file content

* @param fileName

*/

public static void readFileByRandomAccess(String fileName){

RandomAccessFile randomFile = null;

try {

System.out.println("Random read file ");

// open a file using read-only

randomFile = new RandomAccessFile(fileName, "r");

// file length

long fileLength = randomFile.length();

// Start pos

int beginIndex = (fileLength > 4) ? 4 : 0;

//move to beginIndex pos

randomFile.seek(beginIndex);

byte[] bytes = new byte[10];

int byteread = 0;

//each time at most 10 bytes

//length = readbyte

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) {

}

}

}

}

/**

* display inputstream remaining byte number

* @param in

*/

private static void showAvailableBytes(InputStream in){

try {

System.out.println("current inputstream byte number is " + in.available());

} catch (IOException e) {

e.printStackTrace();

}

}

public static void main(String[] args) {

String fileName = "target.txt";

ReadFromFile.readFileByBytes(fileName);

ReadFromFile.readFileByChars(fileName);

ReadFromFile.readFileByLines(fileName);

ReadFromFile.readFileByRandomAccess(fileName);

}

}

//add contents to the end of a file

import java.io.FileWriter;

import java.io.IOException;

import java.io.RandomAccessFile;

/**

*

*/

public class AppendToFile {

/**

* RandomAccessFile

* @param fileName

* @param content

*/

public static void appendMethodA(String fileName,

String content){

try {

// random access a file using rw

RandomAccessFile randomFile = new RandomAccessFile(fileName, "rw");

// byte number

long fileLength = randomFile.length();

//pointer move to the end of the file

randomFile.seek(fileLength);

randomFile.writeBytes(content);

randomFile.close();

} catch (IOException e){

e.printStackTrace();

}

}

/**

* FileWriter

* @param fileName

* @param content

*/

public static void appendMethodB(String fileName, String content){

try {

//open a writer method, use 'true' means to add contents to the file

FileWriter writer = new FileWriter(fileName, true);

writer.write(content);

writer.close();

} catch (IOException e) {

e.printStackTrace();

}

}

public static void main(String[] args) {

String fileName = "target.txt";

String content = "new append!";

//

AppendToFile.appendMethodA(fileName, content);

AppendToFile.appendMethodA(fileName, "append end. n");

//

ReadFromFile.readFileByLines(fileName);

//

AppendToFile.appendMethodB(fileName, content);

AppendToFile.appendMethodB(fileName, "append end. n");

//

ReadFromFile.readFileByLines(fileName);

}

}