Java - InputStream available() method

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Description

The Java InputStream available() method returns an the number of bytes that can be read from this input stream without blocking by the next invocation of a method from this input stream.

Declaration

Following is the declaration for java.io.InputStream.available() method −

 public int available() 

Parameters

NA

Return Value

The method returns the number of bytes that can be read.

Exception

IOException − If an I/O error occurs.

Example - Usage of InputStream available() method

The following example shows the usage of Java InputStream available() method.

InputStreamDemo.java

 package com.tutorialspoint; import java.io.FileInputStream; import java.io.InputStream; public class InputStreamDemo { public static void main(String[] args) throws Exception { InputStream is = null; int i = 0; char c; try { // new input stream created is = new FileInputStream("test.txt"); // read till the end of the stream while((i = is.read())!=-1) { // convert integer to character c = (char)i; // print System.out.println("Character Read: "+c); } } catch(Exception e) { // if any I/O error occurs e.printStackTrace(); } finally { // releases system resources associated with this stream if(is!=null) is.close(); } } } 

Output(Assuming test.txt contains "ABCDEF")

Let us compile and run the above program, this will produce the following result−

 Character Read: A Character Read: B Character Read: C Character Read: D Character Read: E Character Read: F 

Example - Checking Available Bytes in FileInputStream

The following example shows the usage of Java InputStream available() method.

InputStreamDemo.java

 package com.tutorialspoint; import java.io.FileInputStream; import java.io.IOException; import java.io.InputStream; public class InputStreamDemo { public static void main(String[] args) { try (InputStream inputStream = new FileInputStream("example.txt")) { System.out.println("Bytes available: " + inputStream.available()); // Read the first byte int data = inputStream.read(); System.out.println("First byte read: " + (char) data); // Check available bytes again System.out.println("Bytes available after reading one byte: " + inputStream.available()); } catch (IOException e) { e.printStackTrace(); } } } 

Output(if example.txt contains "Hello")

Let us compile and run the above program, this will produce the following result−

 Bytes available: 5 First byte read: H Bytes available after reading one byte: 4 

Explanation

• Uses FileInputStream to read from "example.txt".

• Calls available() before reading, showing the total available bytes.

• Reads one byte, then calls available() again to show the remaining bytes.

Example - Checking Available Bytes in BufferedInputStream

The following example shows the usage of Java InputStream available() method.

InputStreamDemo.java

 package com.tutorialspoint; import java.io.BufferedInputStream; import java.io.FileInputStream; import java.io.IOException; import java.io.InputStream; public class InputStreamDemo { public static void main(String[] args) { try (InputStream inputStream = new BufferedInputStream(new FileInputStream("example.txt"))) { System.out.println("Buffered Stream - Bytes available: " + inputStream.available()); byte[] buffer = new byte[3]; inputStream.read(buffer); // Read 3 bytes System.out.println("After reading 3 bytes, bytes available: " + inputStream.available()); } catch (IOException e) { e.printStackTrace(); } } } 

Output(if example.txt contains "Microservices")

Let us compile and run the above program, this will produce the following result−

 Buffered Stream - Bytes available: 13 After reading 3 bytes, bytes available: 10 

Explanation

• Uses BufferedInputStream (a subclass of InputStream).

• Calls available() before reading.

• Reads 3 bytes from the file.

• Calls available() again to check the remaining unread bytes.