Java - DataOutputStream writeInt(int v) method

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Description

The Java DataOutputStream 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

The method returns the value of the written field.

Exception

IOException − If an I/O error occurs.

Example - Usage of DataOutputStream writeInt(int v) method

The following example shows the usage of Java DataOutputStream writeInt(int v) method. We've created InputStream, DataInputStream, FileOutputStream and DataOutputStream reference. A int[] buf is initialized with some int values. A FileOutputStream object is created. 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 array is fully written into the stream, we've flushed 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.

DataOutputStreamDemo.java

 package com.tutorialspoint; 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("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("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 - Usage of DataOutputStream writeInt(int v) method

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

As a special case, we're closing the stream before writing any value to check if it supports writing values after closing it.

Once int array is fully written into the stream, we've flushed 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.

DataOutputStreamDemo.java

 package com.tutorialspoint; 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("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("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.

Example - Usage of DataOutputStream writeInt(int v) method

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

DataOutputStreamDemo.java

 package com.tutorialspoint; import java.io.DataOutputStream; import java.io.FileOutputStream; import java.io.IOException; public class DataOutputStreamDemo { public static void main(String[] args) { try (FileOutputStream fos = new FileOutputStream("output.dat"); DataOutputStream dos = new DataOutputStream(fos)) { int number = 12345; // Integer value dos.writeInt(number); // Writes 4 bytes System.out.println("Integer written successfully."); } catch (IOException e) { e.printStackTrace(); } } }

Output

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

 Integer written successfully.

Explanation

  • FileOutputStream− Creates a file named "output.dat" for binary writing.

  • DataOutputStream− Wraps FileOutputStream to provide methods for writing primitive types.

  • writeInt(int v) Method− Converts 12345 (0x00003039 in hexadecimal) into 4 bytes. Writes them in big-endian order−

    • Byte 1 (Most Significant Byte): 00

    • Byte 2: 00

    • Byte 3: 30

    • Byte 4 (Least Significant Byte): 39

  • Automatic Resource Management− The try-with-resources statement ensures the stream is automatically closed.

Binary Representation (output.dat)

The integer 12345 (0x00003039) is stored as−

 00000000 00000000 00110000 00111001

(Hex: 00 00 30 39)

java_io_dataoutputstream.htm
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