Java OutputStreamWriter Tutorial
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OutputStreamWriter is a subclass of Writer, it is a bridge that allows you to convert a byte stream into a character stream, or in other words it allows you to convert an OutputStream into a Writer.
Tip: To convert an "OutputStream" into a "Writer" you just need to concatenate these two words to form "OutputStreamWriter" and you will get the solution.
- TODO Link!
- TODO Link!
- TODO Link!
OutputStreamWriter constructors
OutputStreamWriter(OutputStream out) OutputStreamWriter(OutputStream out, String charsetName) OutputStreamWriter(OutputStream out, Charset cs) OutputStreamWriter(OutputStream out, CharsetEncoder enc)
Besides those methods inherited from the superclass, OutputStreamWriter has a few other methods of its own.
| Method | Description |
| String getEncoding() | Returns the name of the character encoding being used by OutputStreamWriter. |
UTF-16 is a quite common encoding for Chinese or Japanese text. In this example we will analyze how to write a file using UTF-16 encoding.
And here is the content to write to the file:
JP日本-八洲
In this example we use UTF-16 OutputStreamWriter to write characters to a file, then use FileInputStream to read each byte of that file.
OutputStreamWriter_UTF16_Ex1.java
package org.o7planning.outputstreamwriter.ex;
import java.io.File;
import java.io.FileInputStream;
import java.io.FileOutputStream;
import java.io.IOException;
import java.io.InputStream;
import java.io.OutputStream;
import java.io.OutputStreamWriter;
import java.nio.charset.StandardCharsets;
public class OutputStreamWriter_UTF16_Ex1 {
private static final String filePath = "/Volumes/Data/test/utf16-file-out.txt";
public static void main(String[] args) throws IOException {
System.out.println(" --- Write UTF-16 File --- ");
write_UTF16_Character_Stream();
System.out.println(" --- Read File as Binary Stream --- ");
readAs_Binary_Stream();
}
private static void write_UTF16_Character_Stream() throws IOException {
File outFile = new File(filePath);
outFile.getParentFile().mkdirs(); // Create parent folder.
// Create OutputStream to write a file.
OutputStream os = new FileOutputStream(outFile);
// Create a OutputStreamWriter
OutputStreamWriter osw = new OutputStreamWriter(os, StandardCharsets.UTF_16);
String s = "JP日本-八洲";
osw.write(s);
osw.close();
}
private static void readAs_Binary_Stream() throws IOException {
InputStream is = new FileInputStream(filePath);
int byteValue;
while ((byteValue = is.read()) != -1) { // Read byte by byte.
System.out.println((char) byteValue + " " + byteValue);
}
is.close();
}
}
Output:
--- Write UTF-16 File --- --- Read File as Binary Stream --- þ 254 ÿ 255 0 J 74 0 P 80 e 101 å 229 g 103 , 44 0 - 45 Q 81 k 107 m 109 2 50
In Java, char data type is 2 bytes in size, and UTF-16 is used to encode the String type. The image below shows the characters on OutputStreamWriter:
We see from the analysis of the bytes on the newly created file: the first 2 bytes (254, 255) are used to mark that this is an UTF-16 encoded text. They are also known as BOM (Byte Order Mark), the next bytes are the same as the bytes on the OutputStreamWriter.
UTF-8 is the world's most popular encoding. It can encode all writings in the world including Chinese characters and Japanese characters. Starting from Java5, UTF-8 is the default encoding for reading and writing files.
UTF-8 files created by Java have no BOM (Byte Order Mark) (The first bytes of the file to mark that this is an UTF-8 file).
OutputStreamWriter_UTF8_Ex1.java
package org.o7planning.outputstreamwriter.ex;
import java.io.File;
import java.io.FileInputStream;
import java.io.FileOutputStream;
import java.io.IOException;
import java.io.InputStream;
import java.io.OutputStream;
import java.io.OutputStreamWriter;
import java.nio.charset.StandardCharsets;
public class OutputStreamWriter_UTF8_Ex1 {
private static final String filePath = "/Volumes/Data/test/utf8-file-out.txt";
public static void main(String[] args) throws IOException {
System.out.println(" --- Write UTF-8 File --- ");
write_UTF8_Character_Stream();
System.out.println(" --- Read File as Binary Stream --- ");
readAs_Binary_Stream();
}
private static void write_UTF8_Character_Stream() throws IOException {
File outFile = new File(filePath);
outFile.getParentFile().mkdirs(); // Create parent folder.
// Create OutputStream to write a file.
OutputStream os = new FileOutputStream(outFile);
// Create a OutputStreamWriter
OutputStreamWriter osw = new OutputStreamWriter(os, StandardCharsets.UTF_8);
String s = "JP日本-八洲";
osw.write(s);
osw.close();
}
private static void readAs_Binary_Stream() throws IOException {
InputStream is = new FileInputStream(filePath);
int byteValue;
while ((byteValue = is.read()) != -1) { // Read byte by byte.
System.out.println((char) byteValue + " " + byteValue);
}
is.close();
}
}
Output:
--- Write UTF-8 File --- --- Read File as Binary Stream --- J 74 P 80 æ 230 151 ¥ 165 æ 230 156 ¬ 172 - 45 å 229 133 « 171 æ 230 ´ 180 ² 178
In Java, char data type is 2 bytes in size, and UTF-16 is used to encode the String type. The image below shows the characters on OutputStreamWriter:
UTF-8 is encoded much more complex than UTF-16, it uses 1, 2, 3 or 4 bytes to store a character. Detailed analysis of the bytes on the newly created UTF-8 file clearly shows that.
| Number of bytes | From | To | Byte 1 | Byte 2 | Byte 3 | Byte 4 | ||
| 1 | U+0000 | 0 | U+007F | 127 | 0xxxxxxx | |||
| 2 | U+0080 | 128 | U+07FF | 2047 | 110xxxxx | 10xxxxxx | ||
| 3 | U+0800 | 2048 | U+FFFF | 65535 | 1110xxxx | 10xxxxxx | 10xxxxxx | |
| 4 | U+10000 | 65536 | U+10FFFF | 1114111 | 11110xxx | 10xxxxxx | 10xxxxxx | 10xxxxxx |
For example, character "日" has code of 26085, in the range [2048,65535], UTF-8 needs 3 bytes to store it.
