Builder: deleteCharAt and replace edit a range in place

deleteCharAt removes a single character by index, and replace(start, end, text) swaps out a whole range for new text, both without ever allocating a separate String. The buffer keeps being edited in place across both calls.

Code

StringBuilder sb = new StringBuilder("Hexlo Warld");
sb.deleteCharAt(1);
sb.replace(0, 3, "Bye");
System.out.println(sb);

Output

Byeo Warld