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Java - DataInputStream readUtf(DataInput in) method
Description
The Java DataInputStream readUTF(DataInput in) method reads in a string that has been encoded using a modified UTF-8 format.
Declaration
Following is the declaration for java.io.DataInputStream.readUTF(DataInput in) method −
public static final String readUTF(DataInput in)
Parameters
NA
Return Value
This method returns an= Unicode string.
Exception
EOFException
UTFDataFormatException
IOException − If an I/O error occurs.
Example 1
The following example shows the usage of Java DataInputStream readUtf(DataInput in) method. We've created InputStream, DataInputStream, FileOutputStream and DataOutputStream reference. A String[] buf is initialized with some string values. A FileOutputStream object is created with a File. Then DataOutputStream is initialized with FileOutputStream object created before. Then string array is iterated to write string values to the dataoutputstream.
Once string 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 readUtf() method, we're reading every value as String. 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; String[] buf = {"Hello", "World!!"}; try { // create file output stream fos = new FileOutputStream("F:\\test.txt"); // create data output stream dos = new DataOutputStream(fos); // for each string in the buffer for (String j:buf) { // write string encoded as modified UTF-8 dos.writeUTF(j); } // force data 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) { // reads characters encoded with modified UTF-8 String k = dis.readUTF(dis); // print System.out.print(k+" "); } } 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 −
Hello World!!
Example 2
The following example shows the usage of Java DataInputStream readUtf(DataInput in) method. We've created InputStream, DataInputStream, FileOutputStream and DataOutputStream reference. A String[] buf is initialized with some String values. A FileOutputStream object is created with a File. Then DataOutputStream is initialized with FileOutputStream object created before. Then String array is iterated to write String values to the dataoutputstream.
Once String 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 readUtf() method, we're reading every value as String. 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; String[] buf = {"Hello", "World!!"}; try { // create file output stream fos = new FileOutputStream("F:\\test.txt"); // create data output stream dos = new DataOutputStream(fos); // for each String in the buffer for (String j:buf) { // write string encoded as modified UTF-8 dos.writeUTF(j); } // force Strings 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) { // reads characters encoded with modified UTF-8 String k = dis.readUTF(dis); // print System.out.print(k+" "); } } 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 readUtf(DataInput in) method. We've created InputStream, DataInputStream, FileOutputStream and DataOutputStream reference. A String[] buf is initialized with some String values. A FileOutputStream object is created with a File. Then DataOutputStream is initialized with FileOutputStream object created before. Then String array is iterated to write String values to the dataoutputstream.
Once String 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 readUtf() method, we're reading every value as String. Now as a special case, we're reading Strings after all Strings are read using readUtf() method. As a result, we can see the readUtf() 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; String[] buf = {"Hello", "World!!"}; try { // create file output stream fos = new FileOutputStream("F:\\test.txt"); // create data output stream dos = new DataOutputStream(fos); // for each String in the buffer for (String j:buf) { // write string encoded as modified UTF-8 dos.writeUTF(j); } // force Strings 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) { // reads characters encoded with modified UTF-8 String k = dis.readUTF(dis); // print System.out.print(k+" "); } System.out.print(dis.readUTF()); } 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 −
Hello World!! java.io.EOFException at java.base/java.io.DataInputStream.readUnsignedShort(DataInputStream.java:345) at java.base/java.io.DataInputStream.readUTF(DataInputStream.java:594) at java.base/java.io.DataInputStream.readUTF(DataInputStream.java:569) at DataInputStreamDemo.main(DataInputStreamDemo.java:48)