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. This is 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, and your progress syncs across the web and the CoddyKit app. The Java Academy course includes 3 lessons in total.
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.
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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. 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. The Java Academy course includes 3 lessons in total.
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, so you can start here or from the beginning and move at your own pace. This is lesson 3 of 3.
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