Java - DataOutputStream writeFloat(float value)

Description

The Java DataOuputStream writeFloat(float v) method converts the float argument to an int using the floatToIntBits method in class Float, and then writes that int value to the underlying output stream as a 4-byte quantity, high byte first. If no exception is thrown, the counter written is incremented by 4.

Declaration

Following is the declaration for java.io.DataOutputStream.writeFloat(float v) method −

public final void writeFloat(float v)

Parameters

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

Once float 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 readFloat() method, we're reading every value as float. 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;
      float[] dbuf = {65.56f,66.89f,67.98f,68.82f,69.55f,70.37f};
      
      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 (float d:dbuf) {
         
            // write float to the data output stream
            dos.writeFloat(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 float
            float c = dis.readFloat();
            
            // 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 −

65.56 66.89 67.98 68.82 69.55 70.37

Example 2

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

Once float 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 readFloat() method, we're reading every value as float. 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;
      float[] dbuf = {65.56f,66.89f,67.98f,68.82f,69.55f,70.37f};
      
      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 (float d:dbuf) {
         
            // write float to the data output stream
            dos.writeFloat(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 float
            float c = dis.readFloat();
            
            // 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 java.base/java.io.DataOutputStream.writeFloat(DataOutputStream.java:242)
	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.

java_dataoutputstream.htm
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