Java .insert()

The .insert() method places a sequence of characters into the StringBuilder and returns a reference to the object.

Syntax

myStringBuilder.insert(index, str);

The index argument is the zero-based index where the characters are to be inserted. If str is a String, a CharSequence*, or a char[] array**, the characters contained are inserted at index and its capacity is increased by the number of characters inserted. For other types, it behaves as if str was first converted to a string by using String.valueOf(str). If index is negative or greater than the length of the sequence, then a StringIndexOutOfBoundsException is thrown.

* For CharSequence arguments, .insert() can have two additional optional int arguments:

myStringBuilder.insert(index, str, start, end)

In this case, .insert() will insert the subsequence defined by the start and end points specified by start and end.

** For char[] arguments, .insert() can have two additional optional int arguments:

myStringBuilder.insert(index, str, start, len)

In this case, .insert() will insert the subsequence defined by the start point and length specified by start and len.

Example

The following example creates a StringBuilder with a specified String and then uses the .insert() method to change it:

import java.util.*;

public class Example {
  public static void main(String[] args)
  {
    StringBuilder str = new StringBuilder("Hello World!");
    System.out.println(str.toString());
    str.insert(6, "to the ");
    System.out.println(str.toString());
  }
}

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This produces the following output:

Hello World!
Hello to the World!

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