Write a method that groups strings by their length. The method should return a map where keys are string lengths (Integer) and values are lists of strings with that length.
Method Signature
public static Map<Integer, List<String>> groupByLength(List<String> strings)
Examples
Example 1:
Input: ["cat", "dog", "apple", "bat"]
Output: {3: ["cat", "dog", "bat"], 5: ["apple"]}
Explanation: Strings are grouped by their length. Three strings have length 3, and one has length 5.
Example 2:
Input: ["a", "bb", "ccc"]
Output: {1: ["a"], 2: ["bb"], 3: ["ccc"]}
Explanation: Each string has a different length, so each gets its own group.
Example 3:
Input: []
Output: {}
Explanation: Empty input returns an empty map.
Example 4:
Input: null
Output: {}
Explanation: Null input returns an empty map.
Example 5:
Input: ["", "a", ""]
Output: {0: ["", ""], 1: ["a"]}
Explanation: Empty strings have length 0 and are grouped together.
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