Game of Life LeetCode solution in Java

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class Solution {
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  public void gameOfLife(int[][] board) {
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    int m = board.length, n = board[0].length;
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    int[][] next = new int[m][n];
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    for (int i = 0; i < m; i++) {
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      for (int j = 0; j < n; j++) {
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        next[i][j] = nextState(board, i, j, m, n);
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      }
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    }
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    for (int i = 0; i < m; i++) {
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      for (int j = 0; j < n; j++) {
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        board[i][j] = next[i][j];
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      }
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    }
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  }
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  public int nextState(int[][] board, int i, int j, int m, int n) {
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    int ones = 0;
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    for (int x = -1; x <= 1; x++) {
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      for (int y = -1; y <= 1; y++) {
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        if (x == 0 && y == 0) {
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          continue;
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        }
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        int a = i + x, b = j + y;
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        if (a >= 0 && a < m) {
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          if (b >= 0 && b < n) {
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            ones += board[a][b];
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          }
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        }
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      }
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    }
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    if (board[i][j] == 0) {
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      return ones == 3 ? 1 : 0;
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    } else {
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      if (ones == 2 || ones == 3) {
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        return 1;
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      } else {
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        return 0;
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      }
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    }
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  }
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}