Building and Reversing Strings in a Loop

To reverse a word in a loop, you walk through it from the first character to the last, but each character gets stuck onto the front of a growing result string, not the back. Picture a stack: the first letter you process ends up buried at the bottom, and the last letter you process sits on top, at the front of the final string. That is why reversal by loop feels like a stack unloading itself — whatever went in last comes out first.

Checking a palindrome works differently: you do not build anything new, you compare. Keep an index i starting at 0 and an index j starting at length - 1. Compare charAt(i) to charAt(j). If they match, move i forward and j backward, and repeat. If every pair matches by the time i and j meet or cross, the string reads the same forwards and backwards. The loop stops once i ≥ j, since going further would just recheck pairs you already confirmed.

This topic sits right after basic string-building loops and right before loops that transform input, because it combines both ideas: one version of the loop builds a new string, the other scans an existing one with two moving indices. The extension case — ignoring spaces and capitalization — connects forward to string methods like toLowerCase and replace, since cleaning the string before comparing is what makes checks like 'A man a plan a canal Panama' succeed instead of failing on a technicality.