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Java StringBuilder

Introduction

Java StringBuilder is a mutable sequence of characters. This means you can add, delete, or change characters within a StringBuilder instance. It is like a growable array of characters. The StringBuilder in Java is a class in the java.lang package. It is used when we need to make a lot of modifications to our strings of characters.

Why use StringBuilder?

Strings in Java are immutable. This means once a string is created, it cannot be changed. Each time we concatenate strings, a new string is created in the memory. This can lead to inefficiency and memory waste, especially when we have to manipulate strings in loops.

StringBuilder, on the other hand, is mutable. It allows us to modify the string without creating a new instance. This is particularly useful for string manipulation operations, as it can significantly improve the performance of your Java program.

Creating a StringBuilder

Creating a StringBuilder instance is simple. You can create an empty StringBuilder or a StringBuilder with an initial string. Here is how you do it:

// Creating an empty builder with the capacity of 16 (default)
StringBuilder sb1 = new StringBuilder();

// Creating a builder with the initial string
StringBuilder sb2 = new StringBuilder("Hello");

// Creating a builder with the specified initial capacity
StringBuilder sb3 = new StringBuilder(50);

Methods in StringBuilder

StringBuilder provides several methods for manipulating strings. Here are some of the most commonly used ones:

append()​

This method is used to append the string representation of any type of data to the sequence.

StringBuilder sb = new StringBuilder("Hello");
sb.append(" World");  // now sb contains "Hello World"

insert()​

This method inserts the string representation of any type of data at the specified position.

StringBuilder sb = new StringBuilder("Hello World");
sb.insert(6, "Beautiful ");  // now sb contains "Hello Beautiful World"

delete() & deleteCharAt()​

These methods are used to delete the characters in a substring of this sequence or at a specific position.

StringBuilder sb = new StringBuilder("Hello Beautiful World");
sb.delete(6, 16);  // now sb contains "Hello World"

sb.deleteCharAt(5);  // now sb contains "HelloWorld"

reverse()​

This method reverses the sequence of characters in this string builder.

StringBuilder sb = new StringBuilder("Hello World");
sb.reverse();  // now sb contains "dlroW olleH"

toString()​

This method returns a string representing the data in this sequence.

StringBuilder sb = new StringBuilder("Hello World");
String str = sb.toString();  // str contains "Hello World"

Conclusion

Java StringBuilder is a powerful class that provides a mutable sequence of characters. It is highly efficient for string manipulation due to its mutable nature. Remember, if you need to modify strings frequently in your program, StringBuilder can be a better choice than the String class. Happy learning!