Java - DataOutputStream writeInt(int value)



Description

The Java DataOuputStream writeInt(int v) method writes a int value to the to the underlying stream as four bytes. The counter written is incremented by 4 on successful invocation of this method.

Declaration

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

public final void writeInt(int v)

Parameters

v − an int value 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 writeInt(int value) method. We've created InputStream, DataInputStream, FileOutputStream and DataOutputStream reference. A int[] buf is initialized with some int values. A FileOutputStream object is created with a File. Then DataOutputStream is initialized with FileOutputStream object created before. Then int array is iterated to write int values using writeInt() method to the dataoutputstream.

Once int 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 readInt() method, we're reading every value as int. 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;
      int[] dbuf = {65,66,67,68,69,70};
      
      try {
         // create file output stream
         fos = new FileOutputStream("F:\\test.txt");
         
         // create data output stream
         dos = new DataOutputStream(fos);
         
         // for each byte in the buffer
         for (int d:dbuf) {
         
            // write int to the data output stream
            dos.writeInt(d);         
         }
         
         // force bytes 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) {
         
            // read int
            int c = dis.readInt();
            
            // print
            System.out.print(c + " ");
         }
         
      } 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 −

65 66 67 68 69 70

Example 2

The following example shows the usage of Java DataInputStream writeInt(int value) method. We've created InputStream, DataInputStream, FileOutputStream and DataOutputStream reference. A int[] buf is initialized with some int values. A FileOutputStream object is created with a File. Then DataOutputStream is initialized with FileOutputStream object created before. As a special case, we're closing the stream before writing any value to check if it supports writing values after closing it.

Then int array is iterated to write int values using writeInt() method to the dataoutputstream. Once int 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 readInt() method, we're reading every value as int. 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;
      int[] dbuf = {65,66,67,68,69,70};
      
      try {
         // create file output stream
         fos = new FileOutputStream("F:\\test.txt");
         
         // create data output stream
         dos = new DataOutputStream(fos);

         // close the stream
         dos.close(); 
		 
         // for each byte in the buffer
         for (int d:dbuf) {
         
            // write int to the data output stream
            dos.writeInt(d);         
         }
         
         // force bytes 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) {
         
            // read int
            int c = dis.readInt();
            
            // print
            System.out.print(c + " ");
         }
         
      } 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.write(Native Method)
	at java.base/java.io.FileOutputStream.write(FileOutputStream.java:318)
	at java.base/java.io.DataOutputStream.writeInt(DataOutputStream.java:197)
	at DataOutputStreamDemo.main(DataOutputStreamDemo.java:30)
Exception in thread "main" java.lang.NullPointerException
	at DataOutputStreamDemo.main(DataOutputStreamDemo.java:60)uu

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

java_dataoutputstream.htm
Advertisements