Introduction

In Java, strings are immutable, meaning once created, their values cannot be changed. To perform modifications like appending, inserting, or deleting characters efficiently, Java provides two classes: StringBuilder and StringBuffer. Both allow the creation of mutable (modifiable) strings, but they differ mainly in synchronization and performance.

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Code: Example of StringBuilder and StringBuffer

public class StringBuilderVsStringBuffer {
public static void main(String[] args) {
// Using StringBuilder
StringBuilder sb = new StringBuilder("Hello");
sb.append(" World");
sb.insert(5, ",");
sb.replace(0, 5, "Hi");
sb.delete(3, 4);
System.out.println("StringBuilder result: " + sb);
// Using StringBuffer
StringBuffer sbf = new StringBuffer("Java");
sbf.append(" Programming");
sbf.insert(4, " Language");
sbf.replace(0, 4, "Core Java");
sbf.delete(5, 9);
System.out.println("StringBuffer result: " + sbf);
}
}

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Explanation of Each Code Part

1. StringBuilder Example

StringBuilder sb = new StringBuilder("Hello");

• Creates a StringBuilder object with the initial string "Hello".
• Strings created using StringBuilder are mutable, meaning you can modify them.

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sb.append(" World");

• Adds " World" to the end of the existing string.
• Result: "Hello World"

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sb.insert(5, ",");

• Inserts a comma at position 5.
• Result: "Hello, World"

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sb.replace(0, 5, "Hi");

• Replaces characters from index 0 to 5 with "Hi".
• Result: "Hi, World"

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sb.delete(3, 4);

• Deletes the character between index 3 and 4.
• Result: "Hi World"

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2. StringBuffer Example

StringBuffer sbf = new StringBuffer("Java");

• Creates a StringBuffer object with the initial string "Java".
• Like StringBuilder, it is mutable, but synchronized, making it thread-safe.

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sbf.append(" Programming");

• Adds " Programming" to the end.
• Result: "Java Programming"

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sbf.insert(4, " Language");

• Inserts " Language" after "Java".
• Result: "Java Language Programming"

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sbf.replace(0, 4, "Core Java");

• Replaces "Java" with "Core Java".
• Result: "Core Java Language Programming"

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sbf.delete(5, 9);

• Deletes characters from index 5 to 9.
• Result: "Core a Language Programming"

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Comparison Table: StringBuilder vs StringBuffer

Feature	StringBuilder	StringBuffer
Introduced In	Java 5	Java 1.0
Synchronization	Not synchronized (not thread-safe)	Synchronized (thread-safe)
Performance	Faster	Slower due to synchronization
Use Case	Single-threaded programs	Multi-threaded programs
Mutability	Mutable	Mutable
Package	java.lang	java.lang

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Conclusion

• Both StringBuilder and StringBuffer allow modification of strings without creating new objects.
• StringBuilder is faster and should be used in single-threaded applications.
• StringBuffer is thread-safe and should be used in multi-threaded environments.
• Choosing between them depends on whether your program requires synchronization or higher performance.

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