- Java.io package classes
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- Java.io - InputStreamReader
- Java.io - LineNumberInputStream
- Java.io - LineNumberReader
- Java.io - ObjectInputStream
- Java.io - ObjectInputStream.GetField
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- io - ObjectOutputStream.PutField
- Java.io - ObjectStreamClass
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- Java.io - Writer
- Java.io package extras
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- Java.io package Useful Resources
- Java.io - Discussion
Java - DataInputStream readFully() method
Description
The Java DataInputStream readFully(byte[] b) method reads bytes from an input stream and allocates those into the buffer array b.
It blocks until the one of the below conditions occurs −
- b.length bytes of input data are available.
- End of file detected.
- If any I/O error occurs.
Declaration
Following is the declaration for java.io.DataInputStream.readFully(byte[] b) method −
public final void readFully(byte[] b)
Parameters
NA
Return Value
This method does not return any value.
Exception
IOException − If any I/O error occurs or the stream has been closed.
EOFException − If this input stream reaches the end before.
Example 1
The following example shows the usage of Java DataInputStream readFully(byte[] b) method. We've created InputStream and DataInputStream references and then initialized them with FileInputStream and DataInputStream objects. In order to initialize DataInputStream(), we requires FileInputStream object. Once objects are created, we're checking if inputStream has content using available() method. Then a bytearray of available bytes is created which is then used in DataInputStream readFully() method, which populates the bytearray completely. Then this bytearray is iterated and printed.
import java.io.DataInputStream; import java.io.FileInputStream; 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; try { // create file input stream is = new FileInputStream("F:\\test.txt"); // create new data input stream dis = new DataInputStream(is); // available stream to be read int length = dis.available(); // create buffer byte[] buf = new byte[length]; // read the full data into the buffer dis.readFully(buf); // for each byte in the buffer for (byte b:buf) { // convert byte to char char c = (char)b; // prints character System.out.print(c); } } catch(Exception e) { // if any error occurs e.printStackTrace(); } finally { // releases all system resources from the streams if(is!=null) is.close(); if(dis!=null) dis.close(); } } }
Assuming we have a text file F:/test.txt, which has the following content. This file will be used as an input for our example program −
Hello World!
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 readFully(byte[] b) method. We've created InputStream and DataInputStream references and then initialized them with FileInputStream and DataInputStream objects. In order to initialize DataInputStream(), we requires FileInputStream object. In this example, we're using a non-existent file and see if readFully() method is throwing exception.
import java.io.DataInputStream; import java.io.FileInputStream; import java.io.FileNotFoundException; 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; try { // create input stream from file input stream is = new FileInputStream("F:\\test1.txt"); // create data input stream dis = new DataInputStream(is); // count the available bytes form the input stream int count = is.available(); // create buffer byte[] bs = new byte[count]; // read data into buffer dis.readFully(bs); // for each byte in the buffer for (byte b:bs) { // convert byte into character char c = (char)b; // print the character System.out.print(c+" "); } } catch(Exception e) { // if any I/O error occurs e.printStackTrace(); } finally { // releases any associated system files with this stream if(is!=null) is.close(); if(dis!=null) dis.close(); } } }
Assuming we are not having a text file F:/test1.txt. This file will be used as an input for our example program −
Output
Let us compile and run the above program, this will produce the following result −
java.io.FileNotFoundException: F:\test1.txt (The system cannot find the file specified) at java.base/java.io.FileInputStream.open0(Native Method) at java.base/java.io.FileInputStream.open(FileInputStream.java:219) at java.base/java.io.FileInputStream.<init&t;(FileInputStream.java:157) at java.base/java.io.FileInputStream.<init&t;(FileInputStream.java:112) at DataInputStreamDemo.main(DataInputStreamDemo.java:14)
Example 3
The following example shows the usage of Java DataInputStream readFully(byte[] b) method. We've created InputStream and DataInputStream references and then initialized them with FileInputStream and DataInputStream objects. In order to initialize DataInputStream(), we requires FileInputStream object. In this example, we're using an empty file and see if readFully() method is throwing exception or able to read an empty file successfully.
import java.io.DataInputStream; import java.io.FileInputStream; import java.io.FileNotFoundException; 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; try { // create input stream from file input stream is = new FileInputStream("F:\\test.txt"); // create data input stream dis = new DataInputStream(is); // count the available bytes form the input stream int count = is.available(); // create buffer byte[] bs = new byte[count]; // read data into buffer dis.readFully(bs); // for each byte in the buffer for (byte b:bs) { // convert byte into character char c = (char)b; // print the character System.out.print(c+" "); } } catch(Exception e) { // if any I/O error occurs e.printStackTrace(); } finally { // releases any associated system files with this stream if(is!=null) is.close(); if(dis!=null) dis.close(); } } }
Assuming we have a text file F:/test.txt, which has no content. This file will be used as an input for our example program −
Output
Let us compile and run the above program, this will produce the following result as empty content−