Java StringBuilder insert() method has 12 overloaded versions. Here are all of its forms:

1. StringBuilder insert(int offset, boolean b) - Inserts the string representation of the boolean argument into this sequence.
2. StringBuilder insert(int offset, char c) - Inserts the string representation of the char argument into this sequence.
3. StringBuilder insert(int offset, char[] str) - Inserts the string representation of the char array argument into this sequence.
4. StringBuilder insert(int index, char[] str, int offset, int len) - Inserts the string representation of a subarray of the str array argument into this sequence.
5. StringBuilder insert(int dstOffset, CharSequence s) - Inserts the specified CharSequence into this sequence.
6. StringBuilder insert(int dstOffset, CharSequence s, int start, int end) - Inserts a subsequence of the specified CharSequence into this sequence.
7. StringBuilder insert(int offset, double d) - Inserts the string representation of the double argument into this sequence.
8. StringBuilder insert(int offset, float f) - Inserts the string representation of the float argument into this sequence.
9. StringBuilder insert(int offset, int i) - Inserts the string representation of the second int argument into this sequence.
10. StringBuilder insert(int offset, long l) - Inserts the string representation of the long argument into this sequence.
11. StringBuilder insert(int offset, Object obj) - Inserts the string representation of the Object argument into this character sequence.
12. StringBuilder insert(int offset, String str) - Inserts the string into this character sequence.

Java StringBuilder insert() Method Example

Below simple program demonstrate the usage of all insert() overloaded methods.

public class InsertExample {
 public static void main(String[] args) {

  // 12 insert overloaded method
  StringBuilder builder = new StringBuilder("javaguides").insert(1, true);
  System.out.println(builder.toString());

  builder = new StringBuilder("javaguides").insert(0, 'J');
  System.out.println(builder.toString());

  char[] chars = { 'd', 'e', 'v', 'e', 'l', 'o', 'p', 'e', 'r' };
  builder = new StringBuilder("javaguides").insert(4, chars);
  System.out.println(builder.toString());

  CharSequence charSequence = new StringBuilder("J2EE/");
  builder = new StringBuilder("javaguides").insert(0, charSequence);
  System.out.println(builder.toString());

  builder = new StringBuilder("javaguides").insert(0, 100.0d);
  System.out.println(builder.toString());

  builder = new StringBuilder("javaguides").insert(0, 100.0f);
  System.out.println(builder.toString());

  builder = new StringBuilder("javaguides").insert(0, 100);
  System.out.println(builder.toString());

  builder = new StringBuilder("javaguides").insert(0, 100l);
  System.out.println(builder.toString());

  builder = new StringBuilder("javaguides").insert(0, new Object());
  System.out.println(builder.toString());

  builder = new StringBuilder("javaguides").insert(0, "ultimate");
  System.out.println(builder.toString());

  builder = new StringBuilder("javaguides").insert(0, chars, 0, chars.length);
  System.out.println(builder.toString());

  builder = new StringBuilder("javaguides").insert(0, charSequence, 0, charSequence.length());
  System.out.println(builder.toString());
 }
}

Output:

jtrueavaguides
Jjavaguides
javadeveloperguides
J2EE/javaguides
100.0javaguides
100.0javaguides
100javaguides
100javaguides
java.lang.Object@15db9742javaguides
ultimatejavaguides
developerjavaguides
J2EE/javaguides

Reference

https://www.javaguides.net/2018/08/java-stringbuilder-class-api-guide.html