Core Java

Closing Java IO Streams

Ensuring the appropriate closure of IO streams is crucial when dealing with Java IO operations, as it plays a vital role in effective resource management and the overall robustness of the code. Let us delve into a practical approach to understanding the Java IO Streams closing.

1. Introduction

Java Input/Output (IO) streams are an essential part of handling data in Java programs. IO streams provide a convenient way to read or write data to and from various sources, such as files, network connections, and in-memory buffers.

1.1 Types of Streams

Java IO streams are categorized into two main types: InputStreams and OutputStreams.

  • InputStreams are designed to handle input operations. They can read data from a variety of sources, including files, network connections, and other input streams. Examples of InputStream classes include FileInputStream, ObjectInputStream, and ByteArrayInputStream.
  • OutputStreams, on the other hand, are used for output operations. They allow you to write data to different destinations, such as files, network connections, and other output streams. Common OutputStream classes include FileOutputStream, ObjectOutputStream, and ByteArrayOutputStream.

1.2 Key Concepts

Understanding the following key concepts is crucial when working with Java IO streams:

  • Byte Streams: Byte streams handle the I/O of raw binary data. They are suitable for all kinds of data, including images, audio, and text.
  • Character Streams: Character streams are designed for I/O of character data. They use Unicode and are suitable for handling text data.
  • Buffering: Buffering is the process of using a buffer to temporarily store data during input or output operations. It helps improve performance by reducing the number of physical I/O operations.

1.3 Closing IO Streams

Properly closing IO streams is essential for resource management and code robustness. Failing to close streams can lead to resource leaks and potential issues with the underlying system resources.

1.3.1 What Happens When IO Streams Aren’t Closed?

When IO streams are not properly closed in a Java program, it can lead to several potential issues and undesirable consequences. Here are some of the common problems associated with failing to close IO streams:

  • Resource Leaks: Open IO streams consume system resources, and not closing them prevents the release of these resources. Over time, this can lead to resource leaks, where the program uses more and more resources without releasing them.
  • File Locking: In the case of file IO, failing to close a file stream might result in file locking. Some operating systems lock files while they are in use, preventing other processes or applications from accessing or modifying them. Properly closing the stream releases the lock.
  • Data Loss or Corruption: If data is being written to an output stream, failure to close the stream may result in incomplete or corrupted data. Closing the stream ensures that all data is properly flushed and written to the destination.
  • Performance Issues: Open streams consume memory, and a large number of unclosed streams can lead to increased memory usage, potentially causing performance degradation. Closing streams promptly helps manage system resources efficiently.
  • Unpredictable Behavior: Failing to close streams may lead to unpredictable behavior in the program. Some data might not be processed or written correctly, and subsequent operations may be affected.
  • File Descriptor Limitations: In systems with file descriptor limits, failing to close streams may reach the maximum allowed limit, causing the program to fail when attempting to open new streams.
  • Security Vulnerabilities: Leaving streams open can expose the program to security vulnerabilities. For example, open network streams may remain connected, posing a security risk, especially in network-related applications.

2. Closing IO Streams

Let’s explore multiple approaches to closing IO streams along with examples:

2.1 Using try-with-resources Statement (Java 7 Onward)

The try-with-resources statement automatically closes resources like IO streams at the end of the statement. It ensures clean and concise code.

package com.javacodegeeks;

try (FileInputStream fis = new FileInputStream("example.txt")) {
  // Perform IO operations
} catch (IOException e) {
  // Handle exceptions

2.1.1 Using try-with-resources with Multiple Resources

Try-with-resources can handle multiple resources simultaneously. This is especially useful when dealing with multiple streams or other AutoCloseable resources.

package com.javacodegeeks;

try (FileInputStream fis = new FileInputStream("input.txt"); FileOutputStream fos = new FileOutputStream("output.txt")) {
  // Perform IO operations
} catch (IOException e) {
  // Handle exceptions

2.1.2 Benefits of Using try-with-resources Statement

  • Automatic Resource Management: The try-with-resources statement automatically manages the closing of resources, ensuring that they are properly released at the end of the block.
  • Conciseness and Readability: The syntax is concise and enhances code readability by reducing the need for explicit resource-closing boilerplate code.
  • Exception Handling: The try-with-resources statement simplifies exception handling by automatically suppressing or handling exceptions that may occur during resource closure.

2.2 Using try-finally Block

Before Java 7, the try-finally block was commonly used to ensure resource closure. Although it’s less concise than try-with-resources, it is still effective.

package com.javacodegeeks;

FileInputStream fis = null;
try {
  fis = new FileInputStream("example.txt");
  // Perform IO operations
} catch (IOException e) {
  // Handle exceptions
} finally {
  try {
    if (fis != null) {
  } catch (IOException e) {
    // Handle exceptions during closing

2.2.1 Benefits of Using try-finally Block

  • Pre-Java 7 Compatibility: The try-finally block is useful for versions of Java before Java 7, where the try-with-resources statement is not available.
  • Explicit Resource Closure: Developers have explicit control over resource closure, allowing them to define custom behavior or handle specific scenarios during the closing process.
  • Resource Cleanup: The try-finally block ensures that resources are cleaned up even if an exception occurs within the try block, making it a reliable option for resource management.
  • Granular Control: Explicitly closing streams provides granular control over the resource management process, allowing developers to implement custom closing logic if needed.
  • Compatibility: This approach is applicable across different Java versions, making it a versatile option for developers working in various environments.
  • Understanding Resource Lifecycle: Explicit closure enhances developers’ understanding of the resource lifecycle and facilitates the identification of potential issues related to resource management.

3. Conclusion

In conclusion, the proper handling of IO streams is a critical aspect of Java programming, influencing the efficiency, reliability, and resource management of applications. We explored various approaches to closing IO streams, each catering to different Java versions and programming preferences. The introduction of the try-with-resources statement in Java 7 marked a significant advancement, offering a concise and elegant way to automatically manage resource closure. This approach has become the preferred method due to its readability and the reduction of boilerplate code. However, for developers working with earlier Java versions, the try-finally block and explicit stream closing remain viable options, providing control over resource management. Additionally, we discussed the convenience of try-with-resources when dealing with multiple resources simultaneously. Regardless of the chosen approach, emphasizing proper resource closure is indispensable to prevent resource leaks, file locking, and other potential issues, ensuring the development of robust and maintainable Java applications. As developers, understanding these various strategies equips us with the flexibility to adapt to different scenarios and adhere to best practices in IO stream management.


An experience full-stack engineer well versed with Core Java, Spring/Springboot, MVC, Security, AOP, Frontend (Angular & React), and cloud technologies (such as AWS, GCP, Jenkins, Docker, K8).
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