StringBuffer vs StringBuilder

Difference Between StringBuffer and StringBuilder in Java

StringBuffer and StringBuilder are both classes in Java that provide mutable sequences of characters, allowing strings to be modified without creating new objects. While they share many similarities, the key difference lies in how they handle synchronization and their intended use cases.

In this guide, we'll compare StringBuffer and StringBuilder to help you understand when to use each one.

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Key Differences Between StringBuffer and StringBuilder

Feature	StringBuffer	StringBuilder
Synchronization	Synchronized (Thread-safe)	Not synchronized (Not thread-safe)
Performance	Slower due to synchronization overhead	Faster due to lack of synchronization
Thread Safety	Safe to use in multithreaded environments	Not safe to use in multithreaded environments
Use Case	When multiple threads may access the same object	When only a single thread is accessing the object
Introduced In	Java 1.0	Java 1.5

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Detailed Comparison

1. Synchronization

• StringBuffer: All methods in StringBuffer are synchronized, which means that multiple threads cannot access the same StringBuffer object simultaneously. This makes StringBuffer thread-safe but introduces a performance overhead due to the synchronization.

• StringBuilder: Methods in StringBuilder are not synchronized, so it is not thread-safe. However, this lack of synchronization makes StringBuilder faster than StringBuffer in single-threaded environments.

Example:

// StringBuffer (Thread-safe)
StringBuffer sb = new StringBuffer("Codes With Pankaj");
sb.append(" Rocks!");

// StringBuilder (Not thread-safe)
StringBuilder sbuilder = new StringBuilder("Codes With Pankaj");
sbuilder.append(" Rocks!");

2. Performance

• StringBuffer: Due to synchronization, StringBuffer is slower than StringBuilder. The performance impact of synchronization is noticeable, especially in scenarios where multiple threads are not required.

• StringBuilder: StringBuilder is faster than StringBuffer because it does not incur the overhead of synchronization. It is ideal for performance-critical applications where thread safety is not a concern.

Example:

// StringBuffer example
StringBuffer buffer = new StringBuffer();
for (int i = 0; i < 10000; i++) {
    buffer.append("Codes With Pankaj");
}

// StringBuilder example
StringBuilder builder = new StringBuilder();
for (int i = 0; i < 10000; i++) {
    builder.append("Codes With Pankaj");
}

3. Thread Safety

• StringBuffer: If your application involves multiple threads that need to modify the same string, StringBuffer is the appropriate choice. Its thread-safe nature ensures that only one thread can modify the string at a time.

• StringBuilder: In a single-threaded environment, or when thread safety is managed externally, StringBuilder is the better option due to its superior performance.

Example:

// Using StringBuffer in a multithreaded environment
StringBuffer buffer = new StringBuffer("Codes With Pankaj");

Runnable task = () -> {
    synchronized (buffer) {
        buffer.append(" Rocks!");
    }
};

Thread t1 = new Thread(task);
Thread t2 = new Thread(task);

t1.start();
t2.start();

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When to Use StringBuffer or StringBuilder

• Use StringBuffer:

  • When you need to modify strings in a multithreaded environment.

  • When thread safety is a priority.

  • Examples: Building log messages in a multithreaded server, handling concurrent data manipulation.

• Use StringBuilder:

  • When you need to modify strings in a single-threaded environment.

  • When performance is a priority and thread safety is not required.

  • Examples: Constructing dynamic SQL queries, manipulating strings in GUI applications.

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Conclusion

StringBuffer and StringBuilder both provide mutable strings, but their main difference lies in synchronization. Use StringBuffer in multithreaded environments where thread safety is essential, and StringBuilder in single-threaded environments where performance is critical.

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