Write a method that removes duplicate String values from a List while preserving the original order of first occurrences. The method should return a new List with unique values only.
Examples:
Input: ['apple', 'banana', 'apple', 'orange', 'banana']
Output: ['apple', 'banana', 'orange']
Explanation: Duplicates removed, first occurrence kept
Input: ['hello', 'world', 'hello']
Output: ['hello', 'world']
Explanation: Second 'hello' is removed
Input: ['a', 'b', 'c']
Output: ['a', 'b', 'c']
Explanation: No duplicates, list unchanged
Input: []
Output: []
Explanation: Empty list remains empty
Apex Code Editor
Welcome to Lightning Challenge!
How It Works
- • Write your solution in the code editor
- • Connect your Salesforce org to test
- • Submit to check if your solution passes
- • Use hints if you get stuck
Contest Alert
🏆 #CodeEveryDay October 2026 (Oct 4–15)Sponsored by FLXBL
Contest runs October 4 - 15. Complete challenges to climb the leaderboard!
Prizes 1 & 2: Salesforce certification exam voucher — won by random drawing, where every point is a ticket. see all prizes
Only the 12 daily challenges shown during this contest count toward points. Earlier dailies don't carry over.