StringBuilder

What Is StringBuilder?

StringBuilder is a class in Java used to create mutable strings.

Unlike String, which is immutable, StringBuilder allows modifying the same object without creating new objects.

StringBuilder = Mutable sequence of characters used for efficient string manipulation

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Simple Example

StringBuilder sb = new StringBuilder("Hello");

sb.append(" World");

System.out.println(sb); // Hello World

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Common StringBuilder Methods

1. append()

Adds text to the end of the string.

StringBuilder sb = new StringBuilder("Java");

sb.append(" Programming");

System.out.println(sb); // Java Programming

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2. insert()

Inserts text at a specified index.

StringBuilder sb = new StringBuilder("Java");

sb.insert(4, " Language");

System.out.println(sb); // Java Language

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3. replace()

Replaces characters between specified indexes.

StringBuilder sb = new StringBuilder("Java Programming");

sb.replace(5, 16, "Language");

System.out.println(sb); // Java Language

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4. delete()

Deletes characters from the string.

StringBuilder sb = new StringBuilder("Java Programming");

sb.delete(4, 16);

System.out.println(sb); // Java

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5. reverse()

Reverses the characters in the string.

StringBuilder sb = new StringBuilder("Java");

sb.reverse();

System.out.println(sb); // avaJ

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6. capacity()

Returns the current capacity of the builder.

StringBuilder sb = new StringBuilder();

System.out.println(sb.capacity()); //16

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7. length()

Returns the number of characters in the string.

StringBuilder sb = new StringBuilder("Java");

System.out.println(sb.length()); //4

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8. charAt()

Returns character at a specified index.

StringBuilder sb = new StringBuilder("Java");

System.out.println(sb.charAt(2)); // v

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9. setCharAt()

Changes character at a specified index.

StringBuilder sb = new StringBuilder("Java");

sb.setCharAt(0, 'R');

System.out.println(sb); // Rava

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10. toString()

Converts StringBuilder to String.

StringBuilder sb = new StringBuilder("Java");

String str = sb.toString();

System.out.println(str); // Java

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Summary

• StringBuilder is mutable
• It allows efficient string manipulation
• It avoids creating multiple objects