Since there is only one line that can constitute with the requirement, we can check it directly without any loops:
private boolean isWin() { int playerTotal = lastPlayer * 3; for (int i = 0; i < SIZE; i++) { if (board[0][i] + board[1][i] + board[2][i] == playerTotal) { return true; } else if (board[i][0] + board[i][1] + board[i][2] == playerTotal) { return true; } } if (board[0][0] + board[1][1] + board[2][2] == playerTotal) { return true; } return false; }