- Java.io package classes
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- Java.io - DataOutputStream
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- Java.io - FileInputStream
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- Java.io - FilterOutputStream
- Java.io - FilterReader
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- Java.io - InputStream
- 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 readDouble() method
Description
The Java DataInputStream readDouble() method reads 8 bytes and returns one double value.
Declaration
Following is the declaration for java.io.DataInputStream.readDouble() method −
public final double readDouble()
Parameters
NA
Return Value
This method returns 8 bytes of input stream, interpreted as double.
Exception
IOException − If an I/O error occurs or the stream has been closed.
EOFException − If the stream reaches the end.
Example 1
The following example shows the usage of Java DataInputStream readDouble() method. We've created InputStream, DataInputStream, FileOutputStream and DataOutputStream reference. A double[] buf is initialized with some double values. A FileOutputStream object is created with a File. Then DataOutputStream is initialized with FileOutputStream object created before. Then double array is iterated to write double values to the dataoutputstream.
Once double 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 readDouble() method, we're reading every value as double. 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; double[] dbuf = {65.56,66.89,67.98,68.82,69.55,70.37}; 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 (double d:dbuf) { // write double to the data output stream dos.writeDouble(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 double double c = dis.readDouble(); // 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 readDouble() method. We've created InputStream, DataInputStream, FileOutputStream and DataOutputStream reference. A double[] buf is initialized with some double values. A FileOutputStream object is created with a File. Then DataOutputStream is initialized with FileOutputStream object created before. Then double array is iterated to write double values to the dataoutputstream.
Once double 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 readDouble() method, we're reading every value as double. 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; double[] dbuf = {65.56,66.89,67.98,68.82,69.55,70.37}; 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 (double d:dbuf) { // write double to the data output stream dos.writeDouble(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 double double c = dis.readDouble(); // 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:42)
Example 3
The following example shows the usage of Java DataInputStream readDouble() method. We've created InputStream, DataInputStream, FileOutputStream and DataOutputStream reference. A double[] buf is initialized with some double values. A FileOutputStream object is created with a File. Then DataOutputStream is initialized with FileOutputStream object created before. Then double array is iterated to write double values to the dataoutputstream.
Once double 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 readDouble() method, we're reading every value as double. Now as a special case, we're reading bytes after all bytes are read using readDouble() method. As a result, we can see the readDouble() 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; double[] dbuf = {65.56,66.89,67.98,68.82,69.55,70.37}; 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 (double d:dbuf) { // write double to the data output stream dos.writeDouble(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 double double c = dis.readDouble(); // print System.out.print(c + " "); } System.out.print(dis.readDouble()); } 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 java.io.EOFException at java.base/java.io.DataInputStream.readFully(DataInputStream.java:202) at java.base/java.io.DataInputStream.readLong(DataInputStream.java:421) at java.base/java.io.DataInputStream.readDouble(DataInputStream.java:473) at DataInputStreamDemo.main(DataInputStreamDemo.java:48)
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