StringBuilder deleteCharAt() function " String index out of range : 6 "

Question

Code and Error

Error 2

hey Guys see the Image and help me out to sort out this issue

It is the first code and it runs perfectly but when i use the same approach in the blow code it have some error " For error detail open image link "

String str = "Samaarth";
StringBuilder sb = new StringBuilder(str);
sb.deleteCharAt(3);
System.out.println(sb.toString());

This is where the error start and the error is because of DeleteCharAt() function but in the above code this function works perfectly but here it is not IDK why so please help me out to sort our this issue

String str= "aaabccddd";

StringBuilder sb = new StringBuilder(str);

for (int i = 0; i < str.length() -1; i++) {
    if (sb.charAt(i) == sb.charAt(i + 1)) {
        sb.deleteCharAt(i);
        //sb.deleteCharAt(i+1);
    }
}

System.out.println(sb.toString());

Answer 1

The problem is you are using for loop and you are actually changing/mutating StringBuilder instance at the same time, so the .length() will not be fixed and eventually you will try to reach non-existing index in your for loop and exception will be thrown.

EDIT:

Add these two lines inside your for loop if statement, just before you invoke deleteCharAt() method:

System.out.println("Value of i is: " + i);
System.out.println("StringBuilder length is: " + sb.length());

"i" represents index you are trying to delete, and sb.length() will display actual length of the StringBuilder.