Keyboard Row LeetCode solution in Java

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class Solution {
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  public String[] findWords(String[] words) {
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    String s1 = "qwertyuiopQWERTYUIOP";
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    String s2 = "asdfghjklASDFGHJKL";
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    String s3 = "zxcvbnmZXCVBNM";
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    ArrayList<String> list = new ArrayList<>();
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    for (int i = 0; i < words.length; i++) {
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      int count1 = 0, count2 = 0, count3 = 0, len = words[i].length();
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      for (int j = 0; j < len; j++) {
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        if (s1.contains(Character.toString(words[i].charAt(j)))) count1++;
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        else if (s2.contains(Character.toString(words[i].charAt(j)))) count2++;
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        else if (s3.contains(Character.toString(words[i].charAt(j)))) count3++;
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        if (count1 == len || count2 == len || count3 == len) list.add(words[i]);
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      }
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    }
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    String ans[] = new String[list.size()];
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    list.toArray(ans);
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    return ans;
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  }
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}