juniorStrings
What is String Concatenation and its performance impact?
Updated Apr 28, 2026
Short answer
Combining strings. Repeated concatenation in a loop is O(n^2) due to constant reallocation.
Deep explanation
Strings are one of the most common data types. Combining strings. Repeated concatenation in a loop is O(n^2) due to constant reallocation. Understanding how they are represented (ASCII/UTF-8/UTF-16) is key to solving character encoding issues.
Real-world example
Storing user names or IDs in an application.
Common mistakes
- Modifying a string inside a long loop without using a StringBuilder/StringBuffer.
Follow-up questions
- What is the time complexity of concatenation?