Difference Between String and StringBuffer in Java
In Java, String is immutable, meaning it cannot change once created, making it less efficient for frequently modified text. Conversely, StringBuffer is mutable and thread-safe, ideal for strings undergoing frequent changes, especially in multi-threaded contexts. Let's understand more!
A string is immutable, meaning once a String object is created, it cannot be altered. On the other hand, a StringBuffer is mutable, allowing modifications like additions, deletions, and alterations without creating new objects each time. This mutability makes StringBuffer significantly more efficient for use cases involving frequent modifications of string content. In this blog, we will understand the differences between them in detail!
Table of Content
- Difference between String and StringBuffer in Java
- What is a String in Java?
- What is a StringBuffer in Java?
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Difference between String and StringBuffer in Java
Below is a table showing the differences between String and StringBuffer in Java
| Aspect |
String |
StringBuffer |
| Mutability |
Immutable - once created, its value cannot be changed. |
Mutable - can be modified after it is created. |
| Performance |
Less efficient in cases where many modifications are needed, as each modification creates a new string. |
More efficient for frequent modifications, as it doesn't create new instances on modification. |
| Thread Safety |
Strings are inherently thread-safe due to immutability. |
StringBuffer is thread-safe and synchronized, ensuring safe use in multi-threaded environments. |
| Memory Usage |
Consumes more memory when altered frequently because every alteration creates a new instance. |
Consumes less memory in a scenario of frequent alterations as it modifies the same instance. |
| Methods |
Limited to operations that don't alter the strings, like concat(), substring(), replace(), which all return new strings. |
Provides methods for altering the content, like append(), insert(), delete(), reverse(), directly altering the buffer. |
What is a String in Java?
In Java, a String is a fundamental data type used to represent and manipulate sequences of characters, essentially text. A String in Java has several key characteristics:
- Immutability: Once a String object is created, its value cannot be changed. If you modify a String, a new String object is created in memory. This immutable nature can enhance performance and security.
- Stored as Object: String in Java is not a primitive data type like int or double, and it's a class, and each String is an instance of this class.
- Literal Creation: You can create a String simply by assigning a string literal, like String s = "Hello";
- String Pool: Java maintains a special memory region called the String Pool, where literals are stored. When a new String is created with the same value as an existing one, Java reuses the object from the pool, which is a part of the heap memory.
- Common Operations: String provides various methods for common text operations, such as concatenation (+), comparison (equals(), compareTo()), searching (indexOf(), contains()), and modification (creating a new string with operations like substring(), replace()).
- Unicode Support: Java String supports Unicode, making it capable of representing a wide range of characters and symbols.
- Length Property: You can obtain the length (number of characters) of a String using the length() method.
What is a StringBuffer in Java?
In Java, StringBuffer is a class used to represent strings that can be modified, contrasting with the immutable String class. Key features of StringBuffer include:
- Mutability: Unlike strings, StringBuffer objects are mutable. This means you can change, add, or remove characters from a StringBuffer object without creating a new one.
- Synchronized for Thread Safety: StringBuffer operations are thread-safe as the methods are synchronized. This means it can be safely used in a multithreaded environment where multiple threads are modifying the same StringBuffer object.
- Dynamic Expansion: A StringBuffer automatically adjusts its capacity (size) when necessary. If the internal buffer overflows, it is automatically made larger to accommodate more characters.
- Performance: Due to its mutability, StringBuffer is more performance-efficient than String when dealing with strings that require frequent modifications. This efficiency comes from avoiding the creation of multiple immutable string objects.
- Common Operations: StringBuffer provides various methods for string manipulation like append() (to add text at the end), insert() (to add text at a specific position), delete() and deleteCharAt() (to remove text), reverse() (to reverse the content), and more.
- Conversion to String: You can convert a StringBuffer back to a String when needed using the toString() method.
Read Later
Thus, the primary difference between String and StringBuffer in Java lies in their mutability and performance characteristics. While String is suitable for text data that remains constant, StringBuffer is preferable when dealing with text that undergoes frequent and complex modifications, especially in multithreaded applications. However, this efficiency comes at the cost of increased complexity due to its mutable and synchronized nature.
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FAQs
What is the main difference between String and StringBuffer?
A String is immutable in Java, meaning once it is created, it cannot be changed or modified. When you try to alter a String, a new String instance gets created. StringBuffer, on the other hand, is mutable, allowing strings to be modified in place without creating a new object every time.
How does thread-safety differ between String and StringBuffer?
StringBuffer is thread-safe, meaning it is designed to be safe when used by multiple threads through synchronized methods. This thread-safety ensures that only one thread can modify the StringBuffer at any given time. In contrast, since String objects are immutable, thread safety is not a concern; they can be shared between threads without issues.
When should you use String instead of StringBuffer?
You should use String when you need immutable character sequences. String is preferred for constants, fixed values, or when you're dealing with a relatively small amount of concatenation operations. Immutable strings reduce errors and offer simplicity in multithreaded environments due to their inherent thread safety.
Why would you choose StringBuffer over String?
StringBuffer is the better choice when you have to make many modifications to a string of characters, especially in a multithreaded environment. The mutable nature of StringBuffer means it's more memory efficient when performing numerous concatenations or alterations because it doesn't create a new object with each change.
Can String and StringBuffer be used interchangeably?
While you can convert between String and StringBuffer using methods like toString() and constructors, they serve different purposes and are not interchangeable in use cases. Choose String for immutable sequences and when thread safety isn't a concern, and StringBuffer for mutable sequences in situations requiring thread safety or extensive modifications.
Hello, world! I'm Esha Gupta, your go-to Technical Content Developer focusing on Java, Data Structures and Algorithms, and Front End Development. Alongside these specialities, I have a zest for immersing myself in v... Read Full Bio
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