Java - DataOutputStream writeShort(short value)

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Description

The Java DataOuputStream writeUTF(String str) method writes a string to the underlying output stream using modified UTF-8 encoding.

Declaration

Following is the declaration for java.io.DataOutputStream.writeUTF(String str) method −

public final void writeUTF(String str)

Parameters

str − a string to be written to the output stream.

Return Value

This method does not return any value.

Exception

IOException − If an I/O error occurs.

Example 1

The following example shows the usage of Java DataInputStream writeUTF() method. We've created InputStream, DataInputStream, FileOutputStream and DataOutputStream reference. A String[] buf is initialized with some string values. A FileOutputStream object is created with a File. Then DataOutputStream is initialized with FileOutputStream object created before. Then string array is iterated to write string values to the dataoutputstream.

Once string arrays is fully written into the stream, we've flush the stream to store the values in the file. Now using FileInputStream and DataInputStream, we're reading the file written earlier. Now we're checking if DataInputStream object has data using available() method. Then using readUTF() method, we're reading every value as String. Finally we're closing all the streams.

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

public class DataOutputStreamDemo {
   public static void main(String[] args) throws IOException {
      InputStream is = null;
      DataInputStream dis = null;
      FileOutputStream fos = null;
      DataOutputStream dos = null;
      String[] buf = {"Hello", "World!!"};
      
      try {
         // create file output stream
         fos = new FileOutputStream("F:\\test.txt");
         
         // create data output stream
         dos = new DataOutputStream(fos);
         
         // for each string in the buffer
         for (String j:buf) {
         
            // write string encoded as modified UTF-8
            dos.writeUTF(j);        
         }
         
         // force data to the underlying stream
         dos.flush();
         
         // create file input stream
         is = new FileInputStream("F:\\test.txt");
         
         // create new data input stream
         dis = new DataInputStream(is);
         
         // read till end of the stream
         while(dis.available()>0) {
         
            // reads characters encoded with modified UTF-8
            String k = dis.readUTF();
            
            // print
            System.out.print(k+" ");
         }
         
      } catch(Exception e) {
         // if any 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 −

Hello World!! 

Example 2

The following example shows the usage of Java DataInputStream writeUTF() method. We've created InputStream, DataInputStream, FileOutputStream and DataOutputStream reference. A String[] buf is initialized with some String values. A FileOutputStream object is created with a File. Then DataOutputStream is initialized with FileOutputStream object created before. Now as a special case, we're closing the stream before writing the values to see if writeUTF method throws exception or not.

Then String array is iterated to write String values to the dataoutputstream. Once String arrays is fully written into the stream, we've flush the stream to store the values in the file. Now using FileInputStream and DataInputStream, we're reading the file written earlier. Now we're checking if DataInputStream object has data using available() method. Then using readUTF() method, we're reading every value as String. Finally we've closed the streams.

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

public class DataInputStreamDemo {
   public static void main(String[] args) throws IOException {
      InputStream is = null;
      DataInputStream dis = null;
      FileOutputStream fos = null;
      DataOutputStream dos = null;
      String[] buf = {"Hello", "World!!"};
      
      try {
         // create file output stream
         fos = new FileOutputStream("F:\\test.txt");
         
         // create data output stream
         dos = new DataOutputStream(fos);
         
         // close the streams
         dos.close();
		 
         // for each String in the buffer
         for (String j:buf) {
         
            // write string encoded as modified UTF-8
            dos.writeUTF(j);         
         }
         
         // force Strings to the underlying stream
         dos.flush();
         
         // create file input stream
         is = new FileInputStream("F:\\test.txt");
         
         // create new data input stream
         dis = new DataInputStream(is);
         
         // read till end of the stream
         while(dis.available()>0) {
         
            // reads characters encoded with modified UTF-8
            String k = dis.readUTF();
            
            // print
            System.out.print(k+" ");
         }
         
      } catch(Exception e) {
         // if any 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:354)
	at java.base/java.io.DataOutputStream.write(DataOutputStream.java:107)
	at java.base/java.io.DataOutputStream.writeUTF(DataOutputStream.java:401)
	at java.base/java.io.DataOutputStream.writeUTF(DataOutputStream.java:323)
	at DataOutputStreamDemo.main(DataOutputStreamDemo.java:30)
Exception in thread "main" java.lang.NullPointerException
	at DataOutputStreamDemo.main(DataOutputStreamDemo.java:60)

As underlying stream FileOutputStream is not supporting write to stream after closing it, we get exception in program execution.