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Java - DataOutputStream writeChar(int v) method

Quiz

Description

The Java DataOutputStream writeChar(int v) method writes a character to the underlying output stream as a two byte value with high byte first. The counter written is incremented by 2 on successful invoking of this method.

Declaration

Following is the declaration for java.io.DataOutputStream.writeChar(int v) method −

public final void writeChar(int v)

Parameters

v − A char value to be written to the stream.

Return Value

This method does not return any value.

Exception

IOException − If an I/O error occurs.

Example - Usage of DataOutputStream writeChar(int v) method

The following example shows the usage of Java DataOutputStream writeChar(int v) method. We've created InputStream, DataInputStream, FileOutputStream and DataOutputStream reference. A byte[] buf is initialized with some byte values. A FileOutputStream object is created. Then DataOutputStream is initialized with FileOutputStream object created before.

We've iterated byte array to write each byte as a char to stream using writeChar(). As next step, stream is flushed. As next step, we've created a FileInputStream object based on file written earlier. Then DataInputStream is initialized with FileInputStream object created. Now dataInputStream is iterated to print the contents. Finally we're closing all the streams.

DataOutputStreamDemo.java

package com.tutorialspoint;

import java.io.IOException;
import java.io.InputStream;
import java.io.DataInputStream;
import java.io.DataOutputStream;
import java.io.FileInputStream;
import java.io.FileOutputStream;

public class DataOutputStreamDemo {
   public static void main(String[] args) throws IOException {
      InputStream is = null;
      DataInputStream dis = null;
      FileOutputStream fos = null;
      DataOutputStream dos = null;
      byte[] buf = {65,66,67,68,69,70};
      
      try {
         // create file output stream
         fos = new FileOutputStream("test.txt");
         
         // create data output stream
         dos = new DataOutputStream(fos);
         
         // for each byte in the buffer
         for (byte b:buf) {
            // write character to the dos
            dos.writeChar(b);
         }
         
         // force bytes to the underlying stream
         dos.flush();
         
         // create file input stream
         is = new FileInputStream("test.txt");
         
         // create new data input stream
         dis = new DataInputStream(is);
         
         // read till end of the stream
         while(dis.available()>0) {
         
            // read character
            char c = dis.readChar();
            
            // print
            System.out.print(c);
         }
         
      } catch(Exception e) {
         // if an I/O error occurs
         e.printStackTrace();
      } finally {
         // releases all system resources from the streams
         if(is!=null)
            is.close();
         if(dos!=null)
            is.close();
         if(dis!=null)
            dis.close();
         if(fos!=null)
            fos.close();
      }
   }
}

Output

Let us compile and run the above program, this will produce the following result −

ABCDEF

Example - Usage of DataOutputStream writeChar(int v) method

DataOutputStreamDemo.java

package com.tutorialspoint;

import java.io.IOException;
import java.io.InputStream;
import java.io.DataInputStream;
import java.io.DataOutputStream;
import java.io.FileInputStream;
import java.io.FileOutputStream;

public class DataOutputStreamDemo {
   public static void main(String[] args) throws IOException {
      InputStream is = null;
      DataInputStream dis = null;
      FileOutputStream fos = null;
      DataOutputStream dos = null;
      byte[] buf = {65,66,67,68,69,70};
      
      try {
         // create file output stream
         fos = new FileOutputStream("test.txt");
         
         // create data output stream
         dos = new DataOutputStream(fos);

         // close the stream
         dos.close();
         
         // for each byte in the buffer
         for (byte b:buf) {
            // write character to the dos
            dos.writeChar(b);
         }
         
         // force bytes to the underlying stream
         dos.flush();
         
         // create file input stream
         is = new FileInputStream("test.txt");
         
         // create new data input stream
         dis = new DataInputStream(is);
         
         // read till end of the stream
         while(dis.available()>0) {
         
            // read character
            char c = dis.readChar();
            
            // print
            System.out.print(c);
         }
         
      } catch(Exception e) {
         // if an I/O error occurs
         e.printStackTrace();
      } finally {
         // releases all system resources from the streams
         if(is!=null)
            is.close();
         if(dos!=null)
            is.close();
         if(dis!=null)
            dis.close();
         if(fos!=null)
            fos.close();
      }
   }
}

Output

Let us compile and run the above program, this will produce the following result −

java.io.IOException: Stream Closed
	at java.base/java.io.FileOutputStream.writeBytes(Native Method)
	at java.base/java.io.FileOutputStream.write(FileOutputStream.java:367)
	at java.base/java.io.DataOutputStream.writeChar(DataOutputStream.java:191)
	at com.tutorialspoint.DataOutputStreamDemo.main(DataOutputStreamDemo.java:31)
Exception in thread "main" java.lang.NullPointerException: Cannot invoke "java.io.InputStream.close()" because "is" is null
	at com.tutorialspoint.DataOutputStreamDemo.main(DataOutputStreamDemo.java:61)

Example - Writing and Reading a Character Using writeChar(int v)

The following example shows the usage of Java DataOutputStream writeChar(int v) method.

DataOutputStreamDemo.java

package com.tutorialspoint;

import java.io.DataOutputStream;
import java.io.DataInputStream;
import java.io.FileOutputStream;
import java.io.FileInputStream;
import java.io.IOException;

public class DataOutputStreamDemo {
   public static void main(String[] args) {
      try {
         // Create a DataOutputStream to write to a file
         FileOutputStream fileOutput = new FileOutputStream("output.dat");
         DataOutputStream dataOutput = new DataOutputStream(fileOutput);

         // Write characters to the file
         dataOutput.writeChar('A');  // Unicode U+0041 (stored as 2 bytes)
         dataOutput.writeChar('B');  // Unicode U+0042 (stored as 2 bytes)
         dataOutput.writeChar('C'); // Unicode U+0043 (stored as 2 bytes)

         // Close the output stream
         dataOutput.close();
         System.out.println("Characters successfully written to output.dat");

         // Read the characters back
         FileInputStream fileInput = new FileInputStream("output.dat");
         DataInputStream dataInput = new DataInputStream(fileInput);

         // Read and print the characters
         System.out.println("First character: " + dataInput.readChar());  // A
         System.out.println("Second character: " + dataInput.readChar()); // B
         System.out.println("Third character: " + dataInput.readChar());  // C

         // Close the input stream
         dataInput.close();
      } catch (IOException e) {
         e.printStackTrace();
      }
   }
}

Output

Let us compile and run the above program, this will produce the following result −

Characters successfully written to output.dat
First character: A
Second character: B
Third character: C

Explanation

Writing Characters

writeChar('A') − Writes two bytes (0x00 41 in UTF-16).
writeChar('B') − Writes two bytes (0x00 42 in UTF-16).
writeChar('C') − Writes two bytes (0x00 43 in UTF-16).

Reading Characters

readChar() correctly retrieves and reconstructs the characters from their two-byte Unicode representation.

java_io_dataoutputstream.htm

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