Alphabet Board Path LeetCode solution in Java

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class Solution {
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  public String alphabetBoardPath(String target) {
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    int x = 0, y = 0;
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    StringBuilder sb = new StringBuilder();
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    for (int i = 0; i < target.length(); i++) {
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      char ch = target.charAt(i);
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      int x1 = (ch - 'a') / 5;
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      int y1 = (ch - 'a') % 5;
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      while (x1 < x) {
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        x--;
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        sb.append('U');
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      }
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      while (y1 > y) {
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        y++;
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        sb.append('R');
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      }
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      while (y1 < y) {
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        y--;
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        sb.append('L');
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      }
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      while (x1 > x) {
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        x++;
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        sb.append('D');
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      }
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      sb.append('!');
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    }
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    return sb.toString();
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  }
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}