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Showing content from https://www.tutorialspoint.com/java/io/datainputstream_readunsignedbyte.htm below:

Java - DataInputStream readUnsignedByte() method

The Java DataInputStream readUnsignedByte() method reads an input byte and returns result which is in the range of 0-255.

Following is the declaration for java.io.DataInputStream.readUnsignedByte() method −

public final int readUnsignedByte()

NA

This method returns unsigned 8 bit value.

• IOException − If any I/O error occurs or the stream has been closed.

• EOFException − If the input stream has reached the ends.

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

Then byte array is iterated to write byte values to the dataoutputstream. Once byte arrays 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 readUnsignedByte() method, we're reading every value as byte. Finally we're closing all the streams.

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 DataInputStreamDemo {
   public static void main(String[] args) throws IOException {
      InputStream is = null;
      DataInputStream dis = null;
      FileOutputStream fos = null;
      DataOutputStream dos = null;
      byte[] b = {-124,126};
      
      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 j:b) {
         
            // write byte to the data output stream
            dos.writeByte(j);         
         }
         
         // 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 8 bit unsigned number
            int c = dis.readUnsignedByte();
            
            // 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();
      }
   }
}

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

132 126 

The following example shows the usage of Java DataInputStream readUnsignedByte() method. We've created InputStream, DataInputStream, FileOutputStream and DataOutputStream reference. A byte[] buf is initialized with some byte values. A FileOutputStream object is created with a File. Then DataOutputStream is initialized with FileOutputStream object created before. Then byte array is iterated to write byte values to the dataoutputstream. Once byte arrays 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 readUnsignedByte() method, we're reading every value as byte.

Now as a special case, we're closing the stream before reading the values to see if this methods throw exception or not. As a result, we can see the available() method throws the exception.

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 DataInputStreamDemo {
   public static void main(String[] args) throws IOException {
      InputStream is = null;
      DataInputStream dis = null;
      FileOutputStream fos = null;
      DataOutputStream dos = null;
      byte[] b = {-124,126};
      
      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 j:b) {
         
            // write byte to the data output stream
            dos.writeByte(j);         
         }
         
         // 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);

         // close the streams
         is.close();
         dis.close();
         
         // read till end of the stream
         while(dis.available()>0) {
         
            // read 8 bit unsigned number
            int c = dis.readUnsignedByte();
            
            // 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();
      }
   }
}

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

java.io.IOException: Stream Closed
	at java.base/java.io.FileInputStream.available0(Native Method)
	at java.base/java.io.FileInputStream.available(FileInputStream.java:330)
	at java.base/java.io.FilterInputStream.available(FilterInputStream.java:167)
	at DataInputStreamDemo.main(DataInputStreamDemo.java:44)

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

Once int arrays 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 readUnsignedByte() method, we're reading every value as byte. Now as a special case, we're reading bytes after all bytes are read using readUnsignedByte() method. As a result, we can see the readUnsignedByte() throws an EOFException.

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 DataInputStreamDemo {
   public static void main(String[] args) throws IOException {
      InputStream is = null;
      DataInputStream dis = null;
      FileOutputStream fos = null;
      DataOutputStream dos = null;
      byte[] b = {-124,126};
      
      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 j:b) {
         
            // write byte to the data output stream
            dos.writeByte(j);         
         }
         
         // 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 8 bit unsigned number
            int c = dis.readUnsignedByte();
            
            // print
            System.out.print(c + " ");
         }
		 System.out.print(dis.readUnsignedByte());
         
      } 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();
      }
   }
}

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

132 126 java.io.EOFException
	at java.base/java.io.DataInputStream.readUnsignedByte(DataInputStream.java:320)
	at DataInputStreamDemo.main(DataInputStreamDemo.java:48)

java_io_datainputstream.htm

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