Group By Property in Java: Explanation & Practice

Problem summary

Write a program that groups words by their first letter.

Starter code

import java.util.*;

public class Main {
    public static void main(String[] args) {
        List<String> words = Arrays.asList("apple", "banana", "apricot", "berry", "avocado"); // Test case 1
        
        // Group by first letter
        // Print: letter: [words]
    }
}

Expected output and test cases

• Grouped by letter

  a: [apple, apricot, avocado]
  b: [banana, berry]

• Different groups

  c: [cat, car]
  d: [dog]

• All same letter

  x: [x, xx, xxx]

Hints

1. Use Map<Character, List<String>>
2. Get first char with charAt(0)
3. computeIfAbsent() for cleaner code

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• Practice Sort Map by Value in Java
• Practice Simple LRU Cache in Java

Practice all Collections exercises · Run this idea in the Java compiler