YouTipJava Dataoutputstream
# Java DataOutputStream Class
[ Java Stream](#)
* * *
The data output stream allows an application to write Java primitive data types to an output stream in a machine-independent way.
The following constructor is used to create a data output stream object.
```java
DataOutputStream out = new DataOutputStream(OutputStream out);
Once the object is successfully created, you can refer to the methods listed below to perform write operations or other operations on the stream.
| No. | Method Description |
| --- | --- |
| 1 | **public final void write(byte[] w, int off, int len) throws IOException** Writes `len` bytes from the specified byte array starting at offset `off` to this byte array output stream. |
| 2 | **public final int write(byte[] b) throws IOException** Writes the specified byte to this byte array output stream. |
| 3 | 1. **public final void writeBoolean() throws IOException,** 2. **public final void writeByte() throws IOException,** 3. **public final void writeShort() throws IOException,** 4. **public final void writeInt() throws IOException** These methods write the specified primitive data type as bytes to the output stream. |
| 4 | **public void flush() throws IOException** Flushes this output stream and forces any buffered output bytes to be written out. |
| 5 | **public final void writeBytes(String s) throws IOException** Writes the string as a byte sequence to the underlying output stream. Each character in the string is written in sequence, and its high eight bits are discarded. |
### Example
The following example demonstrates the use of DataInputStream and DataOutputStream. The example reads 5 lines from a text file `test.txt`, converts them to uppercase, and saves them in another file `test1.txt`.
The content of `test.txt` is as follows:
tutorial1
tutorial2
tutorial3
tutorial4
tutorial5
## Example
```java
import java.io.*;
public class Test {
public static void main(String args[]) throws IOException {
DataInputStream in = new DataInputStream(new FileInputStream("test.txt"));
DataOutputStream out = new DataOutputStream(new FileOutputStream("test1.txt"));
BufferedReader d = new BufferedReader(new InputStreamReader(in));
String count;
while ((count = d.readLine()) != null) {
String u = count.toUpperCase();
System.out.println(u);
out.writeBytes(u + " ,");
}
d.close();
out.close();
}
}
The compilation and execution results of the above example are as follows:
TUTORIAL1 ,
TUTORIAL2 ,
TUTORIAL3 ,
TUTORIAL4 ,
TUTORIAL5 ,
* * Java Stream](#)