In java, a basic input-output stream provides a method for reading & writing bytes or characters in a file.
If we want to read-write primitive data types (such as int, float, etc.) then we can use filter classes to filter data in the original stream.
DataInputStream & DataOutputStream are two filter classes used for creating “data streams” for handling primitive data types.
1 DataInputStream Class
In java DataInputStream class is used to allow applications to read primitive data from different sources.
DataInputStream is a subtype of FilterInputStream.
A. DataInputStream Constructor
| Sr No | Constructor |
|---|---|
| 1 | DataInputStream(InputStream in) Take InputStream object to create DataInputStream |
Constructor call of DataInputStream
FileInputStream i = new FileInputStream("A.txt"); //open file A for read
DataInputStream I = new DataInputStream(i);
B Methods in DataInputStream
Following are the methods of DataInputStream
| Sr No | Method |
|---|---|
| 1 | public final int read(byte[] b) throws IOException Reads number of bytes from input stream and store in buffered array b |
| 2 | public final int read(byte[] b, int off, int len) throws IOException Reads up to len bytes from input stream and store in buffered array b |
| 3 | public final boolean readBoolean() throws IOException Reads one input byte and return true if byte is non zero, else false |
| 4 | public final byte readByte() throws IOException Reads and return one input byte |
| 5 | public final char readChar() throws IOException Reads two input byte and return a char |
| 6 | public final double readDouble() throws IOException Reads eight input byte and return a double value |
| 7 | public final float readFloat() throws IOException Reads four input bytes and return a float value |
| 8 | public final void readFully(byte[] b) throws IOException Reads some bytes from input stream and store in buffer array b |
| 9 | public final int readInt() throws IOException Reads four input bytes and return a integer value |
| 10 | public final long readLong() throws IOException Reads eight input bytes and returns a long value |
| 11 | public final short readShort() throws IOException Reads one input bytes and returns a short value |
| 12 | public final int readUnsignedByte() throws IOException Reads two byte and return unsigned byte value |
| 13 | public final String readUTF() throws IOException Reads a string that has been encoded in modified utf-8 format |
| 15 | public static final String readUTF(DataInput in) throws IOException Reads from a stream that has been encoded in modified utf-8 format |
| 16 | public final int skipBytes(int n) throws IOException Makes attempt to skip n bytes of data from input stream |
Example: dataOutputStream in java Example
1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 | import java.io.DataOutputStream; import java.io.FileNotFoundException; import java.io.FileOutputStream; import java.io.IOException; public class DataOutputStreamExample { public static void main(String[] s) throws FileNotFoundException, IOException { FileOutputStream fos = new FileOutputStream("D:/item.txt"); //Open file “item” for write DataOutputStream dos = new DataOutputStream(fos); String itemName = "Laptop"; dos.writeUTF(itemName); int quantity = 500; dos.writeInt(quantity); double price = 70000; dos.writeDouble(price); System.out.println("Record saved successfully"); dos.close(); fos.close(); } } |
Example: dataInputStream java example
1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 | package com.sspu.javatestproject; import java.io.DataInputStream; import java.io.FileInputStream; import java.io.FileNotFoundException; import java.io.IOException; public class DataInputStreamExample { public static void main(String[] args) throws FileNotFoundException, IOException { FileInputStream fis = new FileInputStream("D:/item.txt"); //open file a for read DataInputStream dis = new DataInputStream(fis); System.out.println("Item Details are"); System.out.println("Item Name " + dis.readUTF()); System.out.println("quantity " + dis.readInt()); System.out.println("price " + dis.readDouble()); dis.close(); fis.close(); } } |
1 2 3 4 5 | name Ram Kumar Item Details are Item Name Laptop quantity 500 price 70000.0 |
Example: Write a program to write & read primitive data on the same file.
Here we discussed DataInputStream and DataOutputStream to read file data.
1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 | import java.io.DataInputStream; import java.io.DataOutputStream; import java.io.FileInputStream; import java.io.FileOutputStream; import java.io.IOException; public class JavaTestProject { public static void main(String args[]) throws IOException { FileOutputStream fos = new FileOutputStream("D:/a.txt"); //Open file “a” for write DataOutputStream dos = new DataOutputStream(fos); //write primitive data on file A String name = "Ram Kumar"; dos.writeUTF(name); int age = 19; dos.writeInt(age); double salary = 130000d; dos.writeDouble(salary); boolean preference = false; dos.writeBoolean(preference); char gender = 'M'; dos.writeChar(gender); dos.close(); fos.close(); //read primitive data from file A FileInputStream fis = new FileInputStream("D:/a.txt"); //open file a for read DataInputStream dis = new DataInputStream(fis); System.out.println("name " + dis.readUTF()); System.out.println("age " + dis.readInt()); System.out.println("salary " + dis.readDouble()); System.out.println("preference " + dis.readBoolean()); System.out.println("gender " + dis.readChar()); dis.close(); fis.close(); } } |
Output
1 2 3 4 5 | name Ram Kumar age 19 salary 130000.0 preference false gender M |
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Which Class Is Used To Read Primitive Data
DataInputStream class is used to read primitive data.
Which Class Is Used To Write Primitive Data to a file
DataOutputStream class is used to write primitive data to file.