Java StringBuilder insert() Method

Java StringBuilder insert() Method | The StringBuilder class in Java contains the insert() method that helps us to insert the string or the character. There are many variations of the insert() method as follows:-

1. public StringBuilder insert(int offset, float flt)
2. public StringBuilder insert(int offset, int i)
3. public StringBuilder insert(int offset, long lng)
4. public StringBuilder insert(int offset, Object objt)
5. public StringBuilder insert(int offset, String string)
6. public StringBuilder insert(int ind, char[ ] array, int offset, int len)
7. public StringBuilder insert(int dstOffset, CharSequence seq)
8. public StringBuilder insert(int dstOffset, CharSequence seq, int begin, int end)
9. public StringBuilder insert(int offset, double dbl)
10. public StringBuilder insert(int offset, boolean bool)
11. public StringBuilder insert(int offset, char c)
12. public StringBuilder insert(int offset, char[ ] array)

Internally the second argument is converted to string and calls insert(int, String) to insert the given values to the StringBuilder object. The “offset” argument must be greater than or equal to 0, and less than or equal to the length of this sequence. Otherwise, it throws StringIndexOutOfBoundsException if the offset is invalid. Let us see the working of some important variations one by one through examples.

StringBuilder Java insert() Method Example

The below program demonstrates the public StringBuilder insert(int offset, boolean bool). The offset value must be greater than or equal to o, and less than or equal to the length of this sequence.

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

      StringBuilder sb = new StringBuilder("Hello  Welcome");
      System.out.println("StringBuilder1 = " + sb);
      sb.insert(6, false);
      System.out.println("After insert = " + sb);
      System.out.println();

      StringBuilder sb1 = new StringBuilder("Two is greater than one? ");
      System.out.println("StringBuilder2 = " + sb1);
      sb1.insert(sb1.length(), true);
      System.out.println("After insert = " + sb1);
   }
}

Output:-

StringBuilder1 = Hello Welcome
After insert = Hello false Welcome

StringBuilder2 = Two is greater than one?
After insert = Two is greater than one? true

StringBuilder insert() Java Example

Let us see another example for StringBuilder insert() Java. We will demonstrate insert(int offset, char c), insert(int offset, char[ ] str), and insert(int dstOffset, CharSequence cs) methods.

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

      StringBuilder sb = new StringBuilder("Jungl");
      System.out.println("StringBuilder1: " + sb);
      char c = 'e';
      // insert(int offset, char c)
      sb.insert(5, c);
      System.out.println("After insert = " + sb);
      System.out.println();

      StringBuilder sb1 = new StringBuilder("Java");
      System.out.println("StringBuilder2: " + sb1);
      char[] array = { 'P', 'r', 'o', 'g', 'r', 'a', 'm' };
      // insert(int offset, char[] str)
      sb1.insert(0, array);
      System.out.println("After insert = " + sb1);
      System.out.println();

      StringBuilder sb3 = new StringBuilder("App");
      System.out.println("StringBuilder3: " + sb3);
      CharSequence ch = "le";
      // insert(int dstOffset, CharSequence cs)
      sb3.insert(3, ch);
      System.out.println("After insert = " + sb3);
   }
}

Output:-

StringBuilder1: Jungl
After insert = Jungle

StringBuilder2: Java
After insert = ProgramJava

StringBuilder3: App
After insert = Apple

If the passed offset value is invalid then insert() methods throw StringIndexOutOfBoundsException. The below Java program demonstrates it:-

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

      StringBuilder sb = new StringBuilder("Learn Java  Language");
      System.out.println("StringBuilder1: " + sb);
      String string = "Programming";
      sb.insert(11, string);
      System.out.println("After insert = " + sb);
      System.out.println();

      StringBuilder sb1 = new StringBuilder("Java");
      System.out.println("StringBuilder2: " + sb1);
      sb1.insert(-5, string);
      System.out.println("After insert = " + sb1);
   }
}

Output:-

StringBuilder1: Learn Java Language
After insert = Learn Java Programming Language

StringBuilder2: Java
Exception in thread “main” java.lang.StringIndexOutOfBoundsException: offset -5, length 4

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