Java Resource Management: Best Practices to Prevent Memory Leaks & Boost Performance

Resource management is a crucial aspect of Java programming, ensuring efficient memory usage and preventing potential issues like memory leaks. Failing to close resources can lead to performance degradation and unexpected behavior in large applications.

Why Close Resources?

Properly closing resources:

️ Prevents memory leaks.

️ Ensures system resources are released.

️ Avoids unexpected crashes and inefficiencies.

Ways to Close Resources in Java

1. Using finally Block (For Java 6 and Earlier)

In older Java versions, resources must be explicitly closed in a finally block to ensure they are released even if an exception occurs:

<span>BufferedReader</span> <span>br</span> <span>=</span> <span>null</span><span>;</span>
<span>try</span> <span>{</span>
    <span>br</span> <span>=</span> <span>new</span> <span>BufferedReader</span><span>(</span><span>new</span> <span>InputStreamReader</span><span>(</span><span>System</span><span>.</span><span>in</span><span>));</span>
    <span>String</span> <span>data</span> <span>=</span> <span>br</span><span>.</span><span>readLine</span><span>();</span>
<span>}</span> <span>catch</span> <span>(</span><span>IOException</span> <span>e</span><span>)</span> <span>{</span>
    <span>e</span><span>.</span><span>printStackTrace</span><span>();</span>
<span>}</span> <span>finally</span> <span>{</span>
    <span>if</span> <span>(</span><span>br</span> <span>!=</span> <span>null</span><span>)</span> <span>{</span>
        <span>try</span> <span>{</span>
            <span>br</span><span>.</span><span>close</span><span>();</span>
        <span>}</span> <span>catch</span> <span>(</span><span>IOException</span> <span>e</span><span>)</span> <span>{</span>
            <span>e</span><span>.</span><span>printStackTrace</span><span>();</span>
        <span>}</span>
    <span>}</span>
<span>}</span>
<span>BufferedReader</span> <span>br</span> <span>=</span> <span>null</span><span>;</span>
<span>try</span> <span>{</span>
    <span>br</span> <span>=</span> <span>new</span> <span>BufferedReader</span><span>(</span><span>new</span> <span>InputStreamReader</span><span>(</span><span>System</span><span>.</span><span>in</span><span>));</span>
    <span>String</span> <span>data</span> <span>=</span> <span>br</span><span>.</span><span>readLine</span><span>();</span>
<span>}</span> <span>catch</span> <span>(</span><span>IOException</span> <span>e</span><span>)</span> <span>{</span>
    <span>e</span><span>.</span><span>printStackTrace</span><span>();</span>
<span>}</span> <span>finally</span> <span>{</span>
    <span>if</span> <span>(</span><span>br</span> <span>!=</span> <span>null</span><span>)</span> <span>{</span>
        <span>try</span> <span>{</span>
            <span>br</span><span>.</span><span>close</span><span>();</span>
        <span>}</span> <span>catch</span> <span>(</span><span>IOException</span> <span>e</span><span>)</span> <span>{</span>
            <span>e</span><span>.</span><span>printStackTrace</span><span>();</span>
        <span>}</span>
    <span>}</span>
<span>}</span>
BufferedReader br = null;
try {
    br = new BufferedReader(new InputStreamReader(System.in));
    String data = br.readLine();
} catch (IOException e) {
    e.printStackTrace();
} finally {
    if (br != null) {
        try {
            br.close();
        } catch (IOException e) {
            e.printStackTrace();
        }
    }
}

Enter fullscreen mode Exit fullscreen mode

2. Using Try-with-Resources (Java 7+)

Introduced in Java 7, try-with-resources automatically closes resources after execution, making code cleaner and reducing the risk of leaks:

<span>try</span> <span>(</span><span>BufferedReader</span> <span>br</span> <span>=</span> <span>new</span> <span>BufferedReader</span><span>(</span><span>new</span> <span>InputStreamReader</span><span>(</span><span>System</span><span>.</span><span>in</span><span>)))</span> <span>{</span>
    <span>String</span> <span>data</span> <span>=</span> <span>br</span><span>.</span><span>readLine</span><span>();</span>
    <span>System</span><span>.</span><span>out</span><span>.</span><span>println</span><span>(</span><span>"You entered: "</span> <span>+</span> <span>data</span><span>);</span>
<span>}</span> <span>catch</span> <span>(</span><span>IOException</span> <span>e</span><span>)</span> <span>{</span>
    <span>e</span><span>.</span><span>printStackTrace</span><span>();</span>
<span>}</span>
<span>try</span> <span>(</span><span>BufferedReader</span> <span>br</span> <span>=</span> <span>new</span> <span>BufferedReader</span><span>(</span><span>new</span> <span>InputStreamReader</span><span>(</span><span>System</span><span>.</span><span>in</span><span>)))</span> <span>{</span>
    <span>String</span> <span>data</span> <span>=</span> <span>br</span><span>.</span><span>readLine</span><span>();</span>
    <span>System</span><span>.</span><span>out</span><span>.</span><span>println</span><span>(</span><span>"You entered: "</span> <span>+</span> <span>data</span><span>);</span>
<span>}</span> <span>catch</span> <span>(</span><span>IOException</span> <span>e</span><span>)</span> <span>{</span>
    <span>e</span><span>.</span><span>printStackTrace</span><span>();</span>
<span>}</span>
try (BufferedReader br = new BufferedReader(new InputStreamReader(System.in))) {
    String data = br.readLine();
    System.out.println("You entered: " + data);
} catch (IOException e) {
    e.printStackTrace();
}

Enter fullscreen mode Exit fullscreen mode

This approach simplifies resource management and enhances code readability.

3. Properly Closing Scanner

When using Scanner, it should be explicitly closed in a finally block to free system resources:

<span>Scanner</span> <span>sc</span> <span>=</span> <span>new</span> <span>Scanner</span><span>(</span><span>System</span><span>.</span><span>in</span><span>);</span>
<span>try</span> <span>{</span>
    <span>System</span><span>.</span><span>out</span><span>.</span><span>println</span><span>(</span><span>"Enter something:"</span><span>);</span>
    <span>String</span> <span>input</span> <span>=</span> <span>sc</span><span>.</span><span>nextLine</span><span>();</span>
    <span>System</span><span>.</span><span>out</span><span>.</span><span>println</span><span>(</span><span>"You entered: "</span> <span>+</span> <span>input</span><span>);</span>
<span>}</span> <span>finally</span> <span>{</span>
    <span>sc</span><span>.</span><span>close</span><span>();</span> <span>// Closing scanner</span>
<span>}</span>
<span>Scanner</span> <span>sc</span> <span>=</span> <span>new</span> <span>Scanner</span><span>(</span><span>System</span><span>.</span><span>in</span><span>);</span>
<span>try</span> <span>{</span>
    <span>System</span><span>.</span><span>out</span><span>.</span><span>println</span><span>(</span><span>"Enter something:"</span><span>);</span>
    <span>String</span> <span>input</span> <span>=</span> <span>sc</span><span>.</span><span>nextLine</span><span>();</span>
    <span>System</span><span>.</span><span>out</span><span>.</span><span>println</span><span>(</span><span>"You entered: "</span> <span>+</span> <span>input</span><span>);</span>
<span>}</span> <span>finally</span> <span>{</span>
    <span>sc</span><span>.</span><span>close</span><span>();</span> <span>// Closing scanner</span>
<span>}</span>
Scanner sc = new Scanner(System.in);
try {
    System.out.println("Enter something:");
    String input = sc.nextLine();
    System.out.println("You entered: " + input);
} finally {
    sc.close(); // Closing scanner
}

Enter fullscreen mode Exit fullscreen mode

Conclusion

Effective resource management is essential for writing robust Java applications. Whether using the finally block in older Java versions or the modern try-with-resources approach, ensuring proper resource closure helps maintain performance and stability. Always close your resources to keep your applications efficient and error-free!

原文链接：Java Resource Management: Best Practices to Prevent Memory Leaks & Boost Performance