- Java.io package classes
- Java.io - Home
- Java.io - BufferedInputStream
- Java.io - BufferedOutputStream
- Java.io - BufferedReader
- Java.io - BufferedWriter
- Java.io - ByteArrayInputStream
- Java.io - ByteArrayOutputStream
- Java.io - CharArrayReader
- Java.io - CharArrayWriter
- Java.io - Console
- Java.io - DataInputStream
- Java.io - DataOutputStream
- Java.io - File
- Java.io - FileDescriptor
- Java.io - FileInputStream
- Java.io - FileOutputStream
- Java.io - FilePermission
- Java.io - FileReader
- Java.io - FileWriter
- Java.io - FilterInputStream
- Java.io - FilterOutputStream
- Java.io - FilterReader
- Java.io - FilterWriter
- Java.io - InputStream
- Java.io - InputStreamReader
- Java.io - LineNumberInputStream
- Java.io - LineNumberReader
- Java.io - ObjectInputStream
- Java.io - ObjectInputStream.GetField
- Java.io - ObjectOutputStream
- io - ObjectOutputStream.PutField
- Java.io - ObjectStreamClass
- Java.io - ObjectStreamField
- Java.io - OutputStream
- Java.io - OutputStreamWriter
- Java.io - PipedInputStream
- Java.io - PipedOutputStream
- Java.io - PipedReader
- Java.io - PipedWriter
- Java.io - PrintStream
- Java.io - PrintWriter
- Java.io - PushbackInputStream
- Java.io - PushbackReader
- Java.io - RandomAccessFile
- Java.io - Reader
- Java.io - SequenceInputStream
- Java.io - SerializablePermission
- Java.io - StreamTokenizer
- Java.io - StringBufferInputStream
- Java.io - StringReader
- Java.io - StringWriter
- Java.io - Writer
- Java.io package extras
- Java.io - Interfaces
- Java.io - Exceptions
- Java.io package Useful Resources
- Java.io - Discussion
Java - DataInputStream readLong() method
Description
The Java DataInputStream readLong() method reads eight input bytes are returns a long value.
Declaration
Following is the declaration for java.io.DataInputStream.readLong() method −
public final long readLong()
Parameters
NA
Return Value
This method returns 8 bytes of input stream, longerpreted as a long value.
Exception
IOException − If an I/O error occurs or the stream is closed.
EOFException − If the input stream reaches the end before the method invocation.
Example 1
The following example shows the usage of Java DataInputStream readLong() method. We've created InputStream, DataInputStream, FileOutputStream and DataOutputStream reference. A long[] buf is initialized with some long values. A FileOutputStream object is created with a File. Then DataOutputStream is initialized with FileOutputStream object created before. Then long array is iterated to write long values to the dataoutputstream.
Once long 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 readLong() method, we're reading every value as long. 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 DataInputStreamDemo { public static void main(String[] args) throws IOException { InputStream is = null; DataInputStream dis = null; FileOutputStream fos = null; DataOutputStream dos = null; long[] buf = {128,250,430,520,820}; 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 (long d:buf) { // write long to the data output stream dos.writeLong(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 long long c = dis.readLong(); // 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 −
128 250 430 520 820
Example 2
The following example shows the usage of Java DataInputStream readLong() method. We've created InputStream, DataInputStream, FileOutputStream and DataOutputStream reference. A long[] buf is initialized with some long values. A FileOutputStream object is created with a File. Then DataOutputStream is initialized with FileOutputStream object created before. Then long array is iterated to write long values to the dataoutputstream. Once long 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 readLong() method, we're reading every value as long. 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.
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; long[] buf = {128,250,430,520,820}; 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 (long d:buf) { // write long to the data output stream dos.writeLong(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); // close the streams is.close(); dis.close(); // read till end of the stream while(dis.available()>0) { // read long long c = dis.readLong(); // 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.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)
Example 3
The following example shows the usage of Java DataInputStream readLong() method. We've created InputStream, DataInputStream, FileOutputStream and DataOutputStream reference. A long[] buf is initialized with some long values. A FileOutputStream object is created with a File. Then DataOutputStream is initialized with FileOutputStream object created before. Then long array is iterated to write long values to the dataoutputstream. Once long 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 readLong() method, we're reading every value as long. Now as a special case, we're reading bytes after all bytes are read using readLong() method. As a result, we can see the readLong() throws an EOFException.
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; long[] buf = {128,250,430,520,820}; 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 (long d:buf) { // write long to the data output stream dos.writeLong(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 long long c = dis.readLong(); // print System.out.print(c + " "); } System.out.print(dis.readLong()); } 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 −
128 250 430 520 820 java.io.EOFException at java.base/java.io.DataInputStream.readFully(DataInputStream.java:202) at java.base/java.io.DataInputStream.readLong(DataInputStream.java:421) at DataInputStreamDemo.main(DataInputStreamDemo.java:48)
To Continue Learning Please Login
Login with Google