Longest Palindrome LeetCode solution in Java

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class Solution {
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  public int longestPalindrome(String s) {
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    HashMap<Character, Integer> map = new HashMap<>();
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    int evenNo = 0;
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    int oddNo = 0;
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    for (int i = 0; i < s.length(); i++) {
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      char c = s.charAt(i);
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      if (map.containsKey(c)) {
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        map.put(c, map.get(c) + 1);
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      } else {
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        map.put(c, 1);
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      }
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    }
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    for (Map.Entry e : map.entrySet()) {
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      int n = (int) e.getValue();
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      if (n % 2 != 0) {
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        oddNo += n;
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      }
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      evenNo += (n / 2) * 2;
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    }
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    if (oddNo > 0) {
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      evenNo += 1;
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    }
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    return evenNo;
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  }
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}