Implement strStr() LeetCode solution in Java

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class Solution {
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  public int strStr(String haystack, String needle) {
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    if (needle.length() > haystack.length()) {
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      return -1;
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    }
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    if (needle.length() == haystack.length()) {
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      if (haystack.equals(needle)) {
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        return 0;
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      }
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      return -1;
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    }
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    int i = 0;
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    int j = 0;
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    while (i < needle.length() && j < haystack.length()) {
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      if (needle.charAt(i) == haystack.charAt(j)) {
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        i++;
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        j++;
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        if (i == needle.length()) {
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          return j - needle.length();
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        }
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      } else {
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        j = j - i + 1; // backtrack to last pos+1 where there was a probable match
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        i = 0;
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      }
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    }
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    return -1;
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  }
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}