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Java DataInputStream Class

In this tutorial, we will learn about DataInputStream in Java. This class reads primitive data from the stream of data without depending on the machine. Java application generally uses the DataOutpuStream to write data that can later be read by a DataInputStream.

Syntax

This is the internal syntax declaration of DataInputStream class.

public class DataInputStream extends FilterInputStream implements DataInput  

Methods

Method Description
int read(byte[] b) It is used to read the number of bytes from the input stream.
int read(byte[] b, int off, int len) It is used to read len bytes of data from the input stream.
int readInt() It is used to read input bytes and return an int value.
byte readByte() It is used to read and return the one input byte.
char readChar() It is used to read two input bytes and returns a char value.
double readDouble() It is used to read eight input bytes and returns a double value.
boolean readBoolean() It is used to read one input byte and return true if byte is non zero, false if byte is zero.
int skipBytes(int x) It is used to skip over x bytes of data from the input stream.
String readUTF() It is used to read a string that has been encoded using the UTF-8 format.
void readFully(byte[] b) It is used to read bytes from the input stream and store them into the buffer array.
void readFully(byte[] b, int off, int len) It is used to read len bytes from the input stream.

Example of DataInputStream class to read data from file

In the program given below, we are reading data from the given file myfile.txt using read() method of DataInputStream class. Firstly we will count the available bytes to read in a file using available() method and create a new byte array of that size. Now we need to read data from a file using the read() method and then we are printing it one by one.

import java.io.DataInputStream;
import java.io.FileInputStream;
import java.io.IOException;
public class StudyTonight 
{
	public static void main(String[] args) throws IOException 
	{ 
		FileInputStream file = new FileInputStream("E:\\studytonight\\myfile.txt");  
		DataInputStream inst = new DataInputStream(file);  
		int count = file.available();  
		byte[] array = new byte[count];  
		inst.read(array);  
		for (byte b : array) {  
			char ch = (char) b;  
			System.out.print(ch);  
		}  
	}  
}


Hello Studytonight

myfile.txt

Hello Studytonight

Example of reading and writing primitive data:

The following example is very important in terms of the actual use of DataInputStream class and DataOutputStream class both, here we will first write the data into a file and the read that data again. When we store the data it will not be in a human-readable form but we can read it properly in a primitive type using DataInputStream.

import java.io.DataInputStream;
import java.io.DataOutputStream;
import java.io.FileInputStream;
import java.io.FileOutputStream;
import java.io.IOException;
public class StudyTonight 
{
	public static void main(String[] args) throws IOException 
	{ 
		DataOutputStream dataOutputStream =	new DataOutputStream(new FileOutputStream("E:\\studytonight\\myfile.txt"));
		dataOutputStream.writeInt(45);
		dataOutputStream.writeFloat(98.7F);
		dataOutputStream.writeLong(123456);
		dataOutputStream.close();
		DataInputStream dataInputStream =new DataInputStream(new FileInputStream("E:\\studytonight\\myfile.txt"));
		int   intData    = dataInputStream.readInt();
		float floatData = dataInputStream.readFloat();
		long  longData    = dataInputStream.readLong();
		dataInputStream.close();
		System.out.println("int data: " + intData);
		System.out.println("float data: " + floatData);
		System.out.println("long data: " + longData);
	}  
}


int data: 45
float data: 98.7
long data: 123456

myfile.txt

   -BÅff     â@

Conclusion

In this tutorial, we learned about DataInputStream class and its methods in Java. This class reads primitive data from the stream of data without depending on the machine.