Sorting/Searching with Collections
Use Collections.sort, Collections.binarySearch, and Comparators for custom sorting and searching.
Sorting/Searching with Collections is a free Java Academy lesson on CoddyKit — lesson 3 of 3. You can read the complete lesson below for free — then practise it hands-on in the browser with a built-in code editor and a 24/7 AI tutor. It is part of the Java Academy learning path, one of 3 lessons in the course, and your progress syncs across the web and the CoddyKit app.
Intro
Sorting organizes data for fast searching. Java's Collections has built-in sort and binarySearch utilities.
Sorting basics
Collections.sort orders a List in-place. By default it uses natural order (e.g., numbers ascending, strings A–Z).
Code: natural sort
Natural order for Integer is ascending. sort() changes the same List.
public class Main {
public static void main(String[] args) {
java.util.List<Integer> nums = new java.util.ArrayList<>();
nums.add(5); nums.add(1); nums.add(3);
java.util.Collections.sort(nums);
System.out.println(nums); // [1,3,5]
}
}
Custom sort
You can pass a Comparator to sort in any order: reverse, by length, or other custom rules.
Code: sort by length
This Comparator sorts strings by their length.
public class Main {
public static void main(String[] args) {
java.util.List<String> words = new java.util.ArrayList<>();
words.add("Java"); words.add("C"); words.add("Python");
java.util.Collections.sort(words, (a,b) -> a.length() - b.length());
System.out.println(words); // [C, Java, Python]
}
}
Code: binarySearch
binarySearch finds the position of an element quickly, but the list must already be sorted consistently.
public class Main {
public static void main(String[] args) {
java.util.List<Integer> nums = new java.util.ArrayList<>();
nums.add(1); nums.add(3); nums.add(5); nums.add(7);
int idx = java.util.Collections.binarySearch(nums, 5);
System.out.println("Index of 5 = " + idx);
}
}
binarySearch check
Quick check: What must be true before using Collections.binarySearch?
Recap
Recap: Use sort() for ordering and binarySearch() for fast lookups. Custom Comparators let you define flexible sorting rules.
Frequently asked questions
Is the “Sorting/Searching with Collections” lesson free?
Yes — the full text of “Sorting/Searching with Collections” is free to read here on the web, and the Java Academy course includes 3 lessons in total. To practise it interactively (a built-in code editor and a 24/7 AI tutor) and unlock the rest of the Java Academy course, upgrade to CoddyKit PRO.
What will I learn in “Sorting/Searching with Collections”?
Use Collections.sort, Collections.binarySearch, and Comparators for custom sorting and searching. You practise Java Academy with hands-on code you run directly in the browser, and a 24/7 AI tutor answers your questions as you work through the lesson.
Do I need any experience to start Java Academy?
No prior experience is required. Java Academy on CoddyKit is structured for beginners through advanced learners; this is — lesson 3 of 3, so you can start here or from the beginning and move at your own pace.
How long does the “Sorting/Searching with Collections” lesson take?
Most CoddyKit lessons take about 5–10 minutes. Each one is bite-sized and interactive, so you make steady progress and pick up exactly where you left off across the web and the app.
Can I write and run code in this Java Academy lesson?
Yes. Every Java Academy lesson includes a built-in code editor, so you write and run real code right in your browser and get instant AI feedback — no local setup required.
All lessons in this course
- Maps & Frequency Counting
- Comparable vs Comparator
- Sorting/Searching with Collections