How do I read and write text files with different character sets?

[Kaydell Leavitt]

I need to be able to read and write text files to and from the following character sets: ASCII, ISO-8809-1, MacRoman, and UTF-8.

I have developed the following code which works, but I don't know how to specify the character set.

Will somebody tell me how to modify my code so that the Charset object that is used can be a parameter?

import java.io.BufferedReader;
import java.io.BufferedWriter;
import java.io.File;
import java.io.FileReader;
import java.io.FileWriter;
import java.io.IOException;
 
// This class is used to read or write to a plain text file.
 
public class PlainTextFile { 
 
private File file;
 
public PlainTextFile(String pathname) {
file = new File(pathname);
}
 
protected String getPath() {
return file.getPath();
}
 
// For writing text files, we'll standardize our apps -- regardless of the platform -- to always use 
// a single LINE_FEED to terminate each line.
// For reading files, the call to BufferedReader.readline() will take care of different line-endings.
 
private BufferedReader br;
private BufferedWriter bw;
 
public void openReader() throws IOException {
if (br == null) {
br = new BufferedReader(new FileReader(file));
} else {
throw new IOException("The TextFile object is already open for reading");
}
}
 
public void closeReader() {
if (br != null) {
try {
br.close();
} catch (IOException e) {
// TODO just log exception that occur while trying to close
} finally {
br = null;
}
}
}

// TODO specify Charset (OK now for Mac-to-Mac)
public void openWriter() throws IOException {
if (bw == null) {
bw = new BufferedWriter(new FileWriter(file));
} else {
throw new IOException("The TextFile object is already open for writing");
}
}

public String readline() throws IOException {
if (br == null) {
throw new IOException("Error: TextFile is not open for reading.");
} else {
String str = br.readLine();
return str;
}
}

public void write(String str) throws IOException {
if (bw == null) {
throw new IOException("Error: TextFile is not open for writing.");
} else {
bw.write(str.toCharArray());
}
}

public void writeChar(char ch) throws IOException {
write("" + ch);
}

public void closeWriter() {
if (bw != null) {
try {
bw.flush();
bw.close();
} catch (IOException e) {
// TODO just log errors that happen when trying to close
} finally {
bw = null;
}
}
}

public void close() {
closeReader();
closeWriter();
}

public static void test01() throws IOException {

// define a constant for the path name to test with
final String FILE_NAME = "TestPlainText.txt";

// test writing to a plain text file
PlainTextFile plainTextFile = new PlainTextFile(FILE_NAME);
plainTextFile.openWriter();
for (char ch = 33; ch <= 127; ch++) {
String string = Character.toString(ch);
plainTextFile.write(string);
}
plainTextFile.close();

// test reading
plainTextFile = new PlainTextFile(FILE_NAME);
plainTextFile.openReader();
String string = plainTextFile.readline();
System.out.println(string);
plainTextFile.close();
}
 
public static void main(String[] args) throws IOException {
test01();
}
 
}

import java.io.IOException;
 
// This class extends the PlainTextFile class and interprets the text file
// as a data file where the fields are separated by a tab and the records
// are separated by a line-feed.
 
public class DataTextFile extends PlainTextFile {
 
// instance variables
// TODO makes these separators parameters
private static final String columnSeparator = "" + 0x09;
private static final String rowSeparator = "" + 0x0A;

public DataTextFile(String pathname) {
super(pathname);
}
 
public void nextColumn() throws IOException {
write(columnSeparator);
}

public void nextRow() throws IOException {
write(rowSeparator);
}

public void writeln(String str) throws IOException {
write(str);
nextRow();
}

public String[] splitLine(String line) {
return line.split(columnSeparator);
}

// This main() method is to test the DataTextFile class, it merely reads the contents
// of a file and displays the contents of the file on the screen.
public static void main(String[] args) throws IOException {

// constant for file name
final String FILE_NAME = "TestPlainText.txt";

// local variable for the object of type DataTextFile
DataTextFile dataTextFile = new DataTextFile(FILE_NAME);

// try to open, read and display the file
try {
// create and open an object of type DataTextFile
dataTextFile.openReader();

// read the document number of the invoice file.
String line;
do {
line = dataTextFile.readline();
if (line != null) {
System.out.println(line);
}
} while (line != null);
dataTextFile.close();
} catch (IOException e) {
System.out.println("There was an error while trying to test the DataTextFile object");
} finally {
if (dataTextFile != null) { dataTextFile.close(); }
}
}

}
package com.kaydell.file;
 
import java.io.IOException;
 
// This class extends the PlainTextFile class and interprets the text file
// as a data file where the fields are separated by a tab and the records
// are separated by a line-feed.
 
public class DataTextFile extends PlainTextFile {
 
// instance variables
// TODO makes these separators parameters
private static final String columnSeparator = "" + 0x09;
private static final String rowSeparator = "" + 0x0A;

public DataTextFile(String pathname) {
super(pathname);
}
 
public void nextColumn() throws IOException {
write(columnSeparator);
}

public void nextRow() throws IOException {
write(rowSeparator);
}

public void writeln(String str) throws IOException {
write(str);
nextRow();
}

public String[] splitLine(String line) {
return line.split(columnSeparator);
}

// This main() method is to test the DataTextFile class, it merely reads the contents
// of a file and displays the contents of the file on the screen.
public static void main(String[] args) throws IOException {

// constant for file name
final String FILE_NAME = "TestPlainText.txt";

// local variable for the object of type DataTextFile
DataTextFile dataTextFile = new DataTextFile(FILE_NAME);

// try to open, read and display the file
try {
// create and open an object of type DataTextFile
dataTextFile.openReader();

// read the document number of the invoice file.
String line;
do {
line = dataTextFile.readline();
if (line != null) {
System.out.println(line);
}
} while (line != null);
dataTextFile.close();
} catch (IOException e) {
System.out.println("There was an error while trying to test the DataTextFile object");
} finally {
if (dataTextFile != null) { dataTextFile.close(); }
}
}

}

[ September 10, 2008: Message edited by: Kaydell Leavitt ]

[Ulf Dittmer]

Instead of FileReader -> BufferedReader you'd use FileInputStream -> InputStreamReader -> BufferedReader. The InputStreamReader constructor can take a CharSet as a parameter. It works similarly for output streams instead of a Writer.